Abstract: A fast rewinding device for cassette tapes in a tape recorder which comprises a main body on which a cassette tape having transparent window means is adapted to be placed and which is provided with a light source and a light receiving element spaced away from and in alignment with said light source so that the light from said light source is received by said light receiving element through the transparent window means. An electrical circuit is provided including a motor for rotating the tape in the rewinding direction, a power source for actuating said motor, a transistor electrically connected between said motor and said power source, a phototransistor adapted to limit electric current to said transistor upon receipt of the light from said light source through said window means, a biasing resistor, a variable resistor for calibrating the circuit and a power source switch for energizing said electrical circuit.