1. A simulator having computer-aided design programs for verifying an algorithm of a shift controller of an automatic transmission mounted on a vehicle having a change-speed system and associated hydraulic actuators to transmit power generated by an internal combustion engine to drive wheels based on at least throttle opening and vehicle speed in accordance with the algorithm, comprising: a computer which stores the computer-aided design programs in memory and connected to the shift controller for inputting the algorithm; pseudo signal generating means connected to the computer for generating pseudo signals indicative of at least the throttle opening, the vehicle speed and operation signals for the hydraulic actuators and for sending the pseudo signals to the computer; wherein the computer-aided design programs include: first calculating means for calculating outputs of a first model describing behavior of the engine, a second model describing behavior of the transmission and a third model describing behavior of a body of the vehicle at a first calculation cycle based on the algorithm and the pseudo signals; second calculating means for inputting at least the calculated outputs of the first model and the second model and for calculating an output of a fourth model describing non-linear behavior in the second model at a second calculation cycle which is shorter than the first calculation cycle; and algorithm verifying means for verifying the algorithm based on the outputs of the first model, the second model and the third model.