A speed converting apparatus with a load controlling function comprises a first interface unit operating for an emulation device according to a system clock of the emulation device, a second interface unit operating for an arithmetic unit according to a system clock of the arithmetic unit, and a load controlling unit controlling at least either a load of a request outputted to the emulation device on the emulation device or a load of a request outputted to the arithmetic unit on the arithmetic unit. In performance verification or connection verification of a target to be verified, the speed converting apparatus can vary a load of a request issued to the target to be verified on the target or a load issued to a verification device on the verification device, while absorbing a difference in operation speed between the target to be verified and the verification device.