A memory module MM, in which a module wiring substrate 5 is equipped with function switching means KK1 and KK2 for arbitrarily switching function switching signals to be inputted to function switching pins FP0 and FP1 of memories 1. By these function switching means KK1 and KK2, moreover, the function switching signals are arbitrarily switched from any of no connection, a supply voltage Vcc and a ground potential Vss. These signals are inputted altogether to all the mounted memories 1 to switch and arbitrarily set functions including reading modes and refresh cycles.