A record medium reproduction unit has a main casing, a transfer device, a pair of sensing pins, a sensing device, and a decision device. The transfer device transfers a larger disk record medium and a smaller disk record medium into and out of the main casing. The sensing pins are movable toward and away from each other and each contact an outer edge of the larger disk record medium when the larger disk record medium enters the main casing. The decision device determines which is inserted into the main casing, the larger disk record medium, the smaller disk record medium, or a special form record medium such as a card-shaped CD based on information supplied from the pair of sensing pins.