This study aims to produce a valid learning device based on guided discovery models to improve mathematical problem-solving ability. Learning tools developed in the form of Lesson Plan (RPP) and Students' Work Sheet (LKPD) of mathematics subject for the class VII of junior high school. The learning model is a guided discovery model that consists of formulating problems, analyzing data, preparing forecasts and providing training. The purpose of the guided discovery model is to engage learners actively in learning activities and bring them gaining more knowledge with their invention. This learning tool uses a Plomp development model consist of 3 phases, namely the preliminary research phase, development or prototyping phase and assessment phase. Learning devices are said to be valid if they meet the validity of content and constructs. The instrument used is a validation sheet containing aspects of presentation, content and material feasibility, graphics or display and language. Expert validation results show that the learning devices were valid.