To provide a self lock clutch suitable for a skew gear with high gear efficiency and capable of securely self-locking with the small number of components.

The self lock clutch includes a shaft member 1 for rotating and driving at a fixed position, a first gear 2 driving around the same shaft center L by the shaft member 1, a second gear 3 rotating at a fixed position by the rotation of the first gear 2 by the relation between the first gear 2 and the skew gear, a lock part 22 provided on both ends of the first gear 2 in the direction of the shaft center L, and power transmission parts 11, 23 between the shaft member 1 and the first gear 2 for allowing relative rotation of the first gear to the shaft member 1 within a range of a certain angle and relative movement to the shaft center L direction within a certain range. When the shaft member 1 rotates and drives, the first gear 2 is engaged with the shaft member 1 at the end part of the certain angle range, and the second gear 3 is rotated by the drive of the first gear 2. When the shaft member 1 does not rotate/drive, the first gear 2 is positioned at the end part of the certain range by the rotation of the second gear 3, and tooth parts 31 of the second gear 3 contact the lock part 22.