A robot program modification system comprises a robot control apparatus and a program modification apparatus. The robot control apparatus has an information acquisition unit which executes an operation program and acquires robot detection information from a robot, and a communication unit which transmits the robot detection information to the program modification apparatus. The program modification apparatus has a simulation unit which performs simulation on the basis of the operation program, and a program modification unit which modifies the operation program on the basis of the robot detection information so that a result of the simulation satisfies an evaluation basis decided in advance.