The purpose of this study was to analyze how children with an intellectual disability acquire subtraction calculation with borrowing using concrete objects. The subject was one girl in the 6th grade who is enrolled in a special needs class at an elementary school. 7 guidance sessions were given during math class. Guidance consisted of learning about types of money and how 1000 yen is made up of 9 100-yen coins and 10 10-yen coins. If a wrong answer was given, the reason for the wrong answer was inquired of the subject. Using semi-concrete objects, equations 1000 - (merchandise price) were shown and the subject was asked to calculate the change using concrete objects. Analysis was conducted based on the right or wrong of the subject’s answer to the problem given by the teacher, verbalizing the process of the subject’s reaching the wrong answer, and the time it took to reach the correct answer. As a result, of the equations 1000 - a 3-digit number, for problems in which the subtracting number was 3 digits or 2 digits other than 0, 1 digits was 0, wrong answers were given until the 5th time. However, right answers were given for the 6th and 7th time and the time required to reach the correct answers decreased. By presenting the equation using semi-concrete objects and by the subject reaching the answer using concrete objects, the concept of tens complement was promoted, leading to the understanding of subtraction calculation with borrowing.