The purpose of this case study is to promote the meta-cognitive strategies of a school boy in Mathematics learning. The participant was a 4th grade boy and he was struggling with math. The researchers focused on issues of his lack of concentration, the use of incorrect algorithm and the difficulties in solving word problems in Mathematics. And we conducted cognitive counseling (Ichikawa,1993) sessions weekly for him. There were 13 sessions for 4 months. These sessions included the training of self-explanation, the lesson induction (Ichikawa,1993), and especially the use of diagrams to solve mathematical word problems. This study adopted the pre- (assessment) and posttest design. As a result, it was found that the posttest scores had increased of 20% over pretest scores. In addition, he could use diagrams increasingly in mathematical word problems and his motivation for math learning was enhanced.