An electromagnetic clutch comprising: a rotor that is formed of a magnetic material and is rotatable by receiving a rotational force from a rotation driving source; an armature plate that is formed of the magnetic material, is connected to a driving shaft for a compressor to be relatively non-rotatable, and is disposed to face a side end surface of the rotor across a slight gap; an excitation coil that is accommodated in the inside of the rotor, forms a magnetic circuit through the rotor and the armature plate by being energized, and generates an attracting force magnetically attracting the armature plate onto the rotor; a temperature fuse that is disposed on the excitation coil side further than the side end surface of the rotor and blocks the electric connection to the excitation coil when exceeding a predetermined temperature; an outer magnetic blocking portion provided on the side end surface of the rotor, which is configured with an annular shape centered on the driving shaft or a plurality of arc shapes disposed on a virtual circle centered on the driving shaft; an inner magnetic blocking portion provided on the side end surface of the rotor, which is configured with an annular shape centered on the driving shaft or a plurality of arc shapes disposed on the virtual circle centered on the driving shaft, which is provided inside further than the outer magnetic blocking portion in a radial direction; and an intermediate magnetic blocking portion provided in the armature plate, which is configured with an annular shape centered on the driving shaft or a plurality of arc shapes disposed on the virtual circle centered on the driving shaft, which is formed in a position facing a position between the outer magnetic blocking portion and the inner magnetic blocking portion in the radial direction, wherein four poles (A, B, C, D)are formed by opposing surfaces formed on outside and inside of each blocking portion of the outer magnetic blocking portion, the intermediate magnetic blocking portion, and the inner magnetic blocking portion in the radial direction by disposing the rotor and the armature plate so as to face each other, characterized in that an annular groove is formed on the side end surface of the rotor so as to include the inner magnetic blocking portion, and wherein a friction member protruding from the side end surface of the rotor is disposed in the annular groove, and wherein the side end surface of the rotor is formed in a center concave shape such that a separation distance from the armature plate is reduced toward the outside in the radial direction during electric disconnection to the excitation coil. a rotor that is formed of a magnetic material and is rotatable by receiving a rotational force from a rotation driving source; an armature plate that is formed of the magnetic material, is connected to a driving shaft for a compressor to be relatively non-rotatable, and is disposed to face a side end surface of the rotor across a slight gap; an excitation coil that is accommodated in the inside of the rotor, forms a magnetic circuit through the rotor and the armature plate by being energized, and generates an attracting force magnetically attracting the armature plate onto the rotor; a temperature fuse that is disposed on the excitation coil side further than the side end surface of the rotor and blocks the electric connection to the excitation coil when exceeding a predetermined temperature; an outer magnetic blocking portion provided on the side end surface of the rotor, which is configured with an annular shape centered on the driving shaft or a plurality of arc shapes disposed on a virtual circle centered on the driving shaft; an inner magnetic blocking portion provided on the side end surface of the rotor, which is configured with an annular shape centered on the driving shaft or a plurality of arc shapes disposed on the virtual circle centered on the driving shaft, which is provided inside further than the outer magnetic blocking portion in a radial direction; and an intermediate magnetic blocking portion provided in the armature plate, which is configured with an annular shape centered on the driving shaft or a plurality of arc shapes disposed on the virtual circle centered on the driving shaft, which is formed in a position facing a position between the outer magnetic blocking portion and the inner magnetic blocking portion in the radial direction, wherein four poles (A, B, C, D)are formed by opposing surfaces formed on outside and inside of each blocking portion of the outer magnetic blocking portion, the intermediate magnetic blocking portion, and the inner magnetic blocking portion in the radial direction by disposing the rotor and the armature plate so as to face each other, characterized in that an annular groove is formed on the side end surface of the rotor so as to include the inner magnetic blocking portion, and wherein a friction member protruding from the side end surface of the rotor is disposed in the annular groove, and wherein the side end surface of the rotor is formed in a center concave shape such that a separation distance from the armature plate is reduced toward the outside in the radial direction during electric disconnection to the excitation coil.