To perform shot blast treatment of the whole face of a product to be treated or the whole treated product uniformly by stopping the rotation of a trough at a forward rotation end and a reverse rotation end and furthermore stopping its rotation by one revolution or more at positions before the forward rotation end and the reverse rotation end, respectively.

A trough 1 of which shape of a cross section of an inner face is half polygonal is topped at a position before a forward rotation end during its forward rotation, and a grinding and cleaning material is ejected from an injection machine 2 provided above the trough 1. Next, the trough 1 is further rotated in the clockwise direction to move a product 3 to be treated slightly to the left direction, and the product 3 to be treated reaches the forward rotation end and is stopped to perform the blast treatment of the right half part thereof. Then, the trough 1 is rotated reversely in the counterclockwise direction and is stopped before the reverse rotation end to invert the product 3 to be treated by 180 degrees. Next, the trough 1 is further rotated reversely in the counterclockwise direction to move the product 3 to be treated slightly to the right direction, and the product 3 to be treated reaches the reverse rotation end and is stopped to blast the left half part thereof. The trough 1 is rotated forwardly in the clockwise direction again to perform the shot blast treatment in the same way.