The purpose of this research was to examine an effective teaching method of probability in the lower elementary education, based on the lesson practice to the first year students. First, the researcher developed a teaching material based on misunderstandings of the students, which were developed from an existing teaching material related to "probability". Second, the effects of the teaching material were analyzed by a questionnaire answered by the students. As a result, it became clear for students to be able to foster the ability to logically think an undetermined event when the following two points were taken into account. First point was that some daily game elements were introduced in the teaching materials and the students were given the situation to deepen their awareness to uncertain events by trials. Second point was to enable the students to focus on numbers and formulas from features of a graph and to give the students chances to experience of fun of awareness that some events in daily lives were demonstrated by numbers and formulas.