To provide a lock confirmation device of a seat capable of confirming incomplete locking of a seat adjuster and preventing the occurrence of inconvenience caused by it.

This lock confirmation device of the seat has sensors 32, 33 for detecting whether operation levers 26, 75 are at lock positions or not, a control part 31 for controlling to restrict a function so that predetermined operation cannot be performed when detection signals indicating that the operation levers 26, 75 are not at lock positions are outputted from each sensor 32, 33, and an informing part 34 for informing whether a locking condition is proper or not based on the detection signals of each sensor 32, 33.