PURPOSE: To stably supply a seat by detecting a fixed dimension mark provided on the seat and stopping a seat feeding means.

CONSTITUTION: A stool seat device 1 has a stool seat frame 5, a taking out port 7 for pulling a seat 6 on which the fixed dimension marks 28 of a fixed interval and a seat feeding means 9 provided on a base body 3 attached to a stool 2 and a control means 11 having a mark sensor 90 for detecting the fixed dimension mark 28 is provided thereon. On the seat 6, the colored and belt shape fixed dimension marks 28 are placed with the intervals of the length capable of covering the stool seat frame 5 determined according to a length between both the end parts of the stool seat frame 5. The mark sensor 90 detects the change of the amount of received light caused by the passing of a fixed dimension mark 28. A control circuit 92 drives the seat feeding means 9 and moves the seat 6 when a switch SW is turned on with the stool seat frame pulled down and unseated and stops motors M, m when the mark sensor 90 detects the fixed dimension mark 28. Thereby, the fixed amount of the seat can be stably supplied at the interval of the mark pitch of the fixed dimension mark.