The Effectiveness of the PBL Model on Mathematics Problem- Solving Ability in Elementary School Mariana Jediut 1 , Elliterius Sennen 2 , Emiliana Nersi 3 {marianajediut90@gmail.com 1 , eliterius63@gmail.com 2 , emiliananersi@gmail.com 3 } 1-3 Universitas Katolik Indonesia Santu Paulus Ruteng, Indonesia Abstract. The background of the research is because of the low problem-solving ability of students in mathematics. This research aims to describe the positive effect and significance of PBL for problem-solving ability of students in SDN Tado Kembo. This research is quantitative. The technique of data collection is a descriptive test. The population of this research is all the students of SDN Tado Kembo. The sample of this research is Students from class V with 40 students divided into 20 control groups and 20 experimental groups. The test result showed that the average learning outcome of the group using PBL was 7,400 while the average learning outcome using the conventional model was 4,650. Furthermore, the researcher did a t-test and the result Tob = 7,481 while Tcv was 1,685. The calculation above showed that Tob > Tcv, then Ho is rejected, and Ha is accepted. This research concludes that PBL can positively and significantly affect the math problem-solving ability of students of SDN Tado Kembo. Keywords: mathematic, problem solving ability 1. Introduction Learning mathematics has to be noticed and taught in schools, from elementary to college. There are so many kinds the purpose for mathematics learning. The other one is to improve student problem-solving capabilities. Problem-solving is the implementation of various methods to complete the problem based on a mathematical model until getting the result [1]. In this case, students can use various strategies to solve the problem. The steps in problem-solving are (1) identifying the various information contained in the problem; (2) The problems formulation and development model of mathematics; (3) implementing the way of problem-solving; (4) reviewing again the result they got [2]. In order to apply the steps, students must understand the questions given to them. Increasing their mathematical problem-solving ability can help students think highly ordinary [3]. However, Indonesian students' problem-solving ability needs to improve nowadays [4]. It is also seen in the results of TIMMS and PISA. The results of TIMSS in 2003rd and 2007 th indicate that it ranked Indonesian Students deeply below other countries [5]. Furthermore, 2015 th TIMMSS results show that Indonesian students' abilities are below level because they can only complete the simple mathematic test [6]. The study result from PISSA proves that 2003rd and 2007 th, where they did every three years, established the rank of Indonesian Students deep below compared to other countries [7]. The same result happened in 2018 th [8]. Indonesian Students do not yet have the ability of high think so they cannot complete the non-routine problem in math. Student ability on SDN Tado Kembo, Manggarai Regency, to complete the math problem is still below. Most students at SDN Tado Kembo need to be more competent in ICEHHA 2022, October 21-22, Ruteng, Indonesia Copyright © 2023 EAI DOI 10.4108/eai.21-10-2022.2329665