The present invention provides a play toy system using a remote-controlled traveling toy, which enables the remote-controlled traveling toy to make a movement that is more unexpected than before, for play. The remote-controlled traveling toy 1 includes one front wheel 5 and two rear wheels 7 and 9. The traveling toy is remotely controlled by remote control signals and is so constructed as to travel on a traveling surface of a play board. The diameter sizes of the two rear wheels 7 and 9 are different. With one front wheel 5 and two rear wheels 7, 9 having a different diameter, the remote-controlled traveling toy 1 can move most unexpectedly that anyone has ever experienced, according to the state of the traveling surface of the play board.