To reduce a manufacturing cost of a wind power generation device having a windmill of large bore.

The wind power generation device comprises: a rotary vanes 12 erected at equal intervals; a supporting body which supports the rotary vanes from a lower surface; a machine room 14 arranged at a rotating center of the rotary vanes 12 via supporting arms 13; a generator 15 stored inside the machine room 14; a supporting column 16 which rotatably supports the machine room 14; and an accelerating mechanism 27 which increases a speed of rotation of the machine room 14 to transmit it to the generator 15. Since the rotary vanes 12 catches wind to integrally rotate the supporting body, the supporting arms 13, and the machine room 14 thereby rotating the generator, strength of the supporting column 16 and the like can be lowered by a supporting force from the supporting body, thereby reducing the manufacturing cost.