Problem-based learning (PBL) is an effective teaching-learning strategy for enhancing students' motivation, problem solving ability, and creativity. Its educational values coincide with the aim of open-inquiry activity introduced in 2007 revised national curriculum. From this aspect we designed the PBL open-inquiry program and implemented to 202 first year middle school students in Gyeonggi provincial office of education for one semester. We developed an energy related PBL problem. The program was designed in four steps: 'understand the problem,' 'investigate information,' 'solve the problem,' and 'present and evaluate the result.' Through the program, students did such activities as 'make Know/need to know chart,' 'group discussion,' 'search information,' and 'preparation of group report.' After completing the program, a survey was conducted to understand the students' perception of the program. The results are as follows: First, 40.6% of students showed positive attitude toward the program. Especially, students responded that 'make Know/need to know chart' was very useful. However, some students responded that 'search information' and 'preparation of group report' were difficult to perform. Second, male students showed positive attitude toward the PBL program compared to female students. Also students had higher scores in attitude toward science, showed more positive attitude toward the PBL program. Third, there was a significant correlation between attitude toward science and perception of PBL steps. Based on survey results, some suggestions were made for teachers who were planning to implement PBL in open-inquiry program.