To provide a saw chain stretching device for a chain saw which is low-priced and can be easily operated without a hindrance by a chain guide plate and can be simply adjusted to the change in an operating position for an operator through his adjustment procedures.

This saw chain stretching device 1 is held between a side case 2 and a body case 22 and adjusts the position of a chain guide plate 4 projecting from a gap between both cases 2, 22. In addition, the device 1 is equipped with a threaded bar member 9 with a head part 10 formed on one of the ends and a pin member 16 which moves the position of the chain guide plate 4 with the body case 22 through moving in the axial direction of the pin member 16 by rotation of the threaded member 9. On the threaded bar member 9, a driven bevel gear 23 is fixed to the end part opposite to the head part 10, in the axial direction O-0, and a drive bevel gear 23 with a shaft part 24 supported pivotally, in a freely rotating manner, on the side case 2, is engaged with the driven bevel gear 23. In addition, the rotary operating part 24b of the shaft part 24a is exposed to the outside of the side case 2.