The purpose of this study is to search a possibility of desirable didactical situations for intuitive probability by designing and applying its mathematics lesson based on Brousseau’s theory of didactial situations(TDS). Based on my critical analysis on the didactical situations suggested by some precedent studies, I tried to design a didactical situation which makes the most of the intention of TDS through referring Brousseau’s lesson case so-called ‘the course to 20’. To do this, one-to-one game, team game, sharing strategies, and teacher’s intervention were designed respectively as situation of action, situation of formulation, situation of validation, and situation of institutionalization using Roller Derby game. I applied these situations to 18 fifth grade students and recognized their intuitive conceptions and misconceptions of probability by analyzing their game boards, their spoken words and discussion, and their discovered strategies through four phased situations. Furthermore, several didactical implications were induced for designing mathematics lessons based on TDS.