A rotary electric shaver in which multiple blade units having an outer blade whose upper surface serves as an annular shaving surface (22A, 22B) and an inner blade coming into sliding contact with a lower surface of the outer blade are arranged in a head unit held in a main body, and in which the outer blade and the inner blade are respectively and rotatably driven, the rotary electric shaver comprising: a gear case that is arranged inside the head unit; a multi-stage structure lower gear that is arranged in a lower portion of the gear case, and that coaxially has an outer blade gear to which driving power is input from a drive source accommodated in the main body and which outputs the driving power to the outer blade, and an inner blade gear which outputs the driving power to the inner blade; an upper gear that is arranged in an upper portion of the gear case, and that outputs the driving power to the outer blade; and a transmission gear that has an input gear which is arranged in the lower portion of the gear case and to which the driving power is input from the lower gear, and an output gear which is arranged in the upper portion of the gear case and which outputs the driving power to the upper gear, in which the input gear and the output gear are coaxially and rotatably connected to each other, and in which a rotary shaft thereof is arranged so as to vertically penetrate the gear case from the lower portion to the upper portion thereof, wherein the driving power from the upper gear drives an outer blade drive gear which drives the outer blade. characterized in that the rotary electric shaver further comprises a pin that has a flange-shaped portion which extends in the radial direction in one end portion, wherein the lower gear, into which the pin is rotatably inserted and which is retained by the flange-shaped portion, and the upper gear, into which the other end portion of the pin is press-fitted, are arranged so as to interpose the gear case therebetween, and are respectively and rotatably held in the gear case by the pin. a gear case that is arranged inside the head unit; a multi-stage structure lower gear that is arranged in a lower portion of the gear case, and that coaxially has an outer blade gear to which driving power is input from a drive source accommodated in the main body and which outputs the driving power to the outer blade, and an inner blade gear which outputs the driving power to the inner blade; an upper gear that is arranged in an upper portion of the gear case, and that outputs the driving power to the outer blade; and a transmission gear that has an input gear which is arranged in the lower portion of the gear case and to which the driving power is input from the lower gear, and an output gear which is arranged in the upper portion of the gear case and which outputs the driving power to the upper gear, in which the input gear and the output gear are coaxially and rotatably connected to each other, and in which a rotary shaft thereof is arranged so as to vertically penetrate the gear case from the lower portion to the upper portion thereof, wherein the driving power from the upper gear drives an outer blade drive gear which drives the outer blade. characterized in that the rotary electric shaver further comprises a pin that has a flange-shaped portion which extends in the radial direction in one end portion, wherein the lower gear, into which the pin is rotatably inserted and which is retained by the flange-shaped portion, and the upper gear, into which the other end portion of the pin is press-fitted, are arranged so as to interpose the gear case therebetween, and are respectively and rotatably held in the gear case by the pin.