A At the gym the number of the users are more than the coach is often occur, so that the result of the exercise was not optimal. To solve that problem, it takes additional cost for hiring additional trainers. To get the maximum result from exercise without additional cost, therefore a device named assisting device for fitness trainer is designed to resolve this problem. In the assisting device for fitness trainer, there are three types of exercise program which is high, medium, and low which contain the same types of exercise with different number of traning session. The users has to choose one of the three types of exercise program to start the exercise program. Before the exercise program was begun, users has to input their personal data using the personal computer. After the exercise program was finish, the result of their exercise can be printed. From the result of the test and the analysis, every module from designing the assisting device for fitness trainer can work well. The microcontroller instrument can work accordance with the programs that have been made. The buzzer instrument work as an indikator to start or end the exercise program can work well. Transmitter and receiver of infrared sensor can work properly in detecting an object that crossing the zone of the sensors. Both of the switches which OK and CANCEL can work well. The LCD can display the text accordance with the programs that have be ,n made.