A car-mounted device control system is obtained which can prevent or lessen erroneous operation of operating portions, switches, and the like during rotation of a steering wheel. When a CPU 16 starts up a function switching program from a storage medium 24 on the basis of an inputted touch signal, a present center control unit 10 compares a comparative rotational position R0 read from the storage medium 24 and a rotational position detection signal R from a steering angle sensor 32. As a result, when the rotational position detection signal R exceeds the comparative rotational position R0, a touch signal and a click signal are cancelled. Thus, inadvertent switching of functions due to a body touching a controller 70 while a steering wheel 22 is rotated can be prevented.