This independent study aimed to develop counting skill of the child with down’s syndrome using magic countable number box. The case study was a 9 years old male student who was diagnosed with down’s syndrome at learnable level with IQ between 62-63. The instruments included number counting magic box, 10 individualized instructional plans for developing number counting skill, pretest and posttest, a learning behavior observation form, and video recorder used to record the case study while engaged in the activities of each instructional plan. Collected data were analyzed in terms of percentage, mean, and analytical description. The findings revealed that 1) the number counting magic box could develop counting skill the case study with 5.2 average increasing score or 52 %, and, 2) results of evaluating learning behavior of the case study during studying using number counting magic box on each of the plan revealed that the score for learning behavior during studying using number counting magic box along the 10 instructional plans was between fair – good quality levels with average score of 8.33 which was at good quality.