To provide a holding checking method and an unholding checking method, which have good productivity and prevent destruction of an object.

After a pair of vertically movable V-blocks is manually or automatically moved upward and downward, so that a turning core of material wood 1 can be obtained, oil and the like flow into a suction port 7a of a cylinder 7, so that a holding member 5 can be moved in the direction of an arrow. ON and OFF signals are output from a rotary encoder 9, for example, at a time interval of 0.05 sec during movement, and the material wood is held by a pawl 5a. When the holding member 5 is stopped, the signal from the rotary encoder 9 is kept in an OFF or ON state. When the OFF or ON state is maintained for a 0.075 sec or more, a controller determines that the holding member 5 holds the material wood 1.