This paper is a case report of cognitive counseling for a junior high school student. Authors instructed a second year female student who had a difficulty in the calculation of positive and negative number and the linear equation. We first instructed the way of calculating, and second we taught how to deal with letters which represent constants in the equation. In addition, the instruction of writing intermediate expressions to reach the lesson induction was conducted. By these instructions, her performances of calculation have improved, and she has been able to use intermediate expression effectively. Moreover, a way of dealing with mathematics became more positive. There were some fields, however, where her understanding has not reached sufficient level by our treatment. It is necessary to improve the method of intervention, - for example, starting with the instruction in the procedure of calculation, depending on the level of understanding of a client.