To provide an operation confirmation device of a water pressure release apparatus, which enables the visual confirmation of the operation of the water pressure release apparatus without sacrificing crime prevention.

This water pressure release apparatus comprises: a water injection port 10 which is formed in a slat 40; a casing 8 which is provided on the indoor side of the slat 40 in the state of communicating with the water injection port 10; an unlocking shaft 9 which is subjected to the release of restrictions on protrusion by water injection, so as to protrude from the casing 8 and perform unlocking; and an operation mechanism which is internally mounted in the casing 8 so as to release the restrictions on the protrusion of the unlocking shaft 9 by water injection. The operation mechanism has a movable element which is moved to the side of a lock body by water injection, and an unlocking marker M is provided in the movable element or an extension portion which is provided in the movable element. In the slat 40, an operation confirmation hole H is formed in a position to enable the visual recognition of the unlocking marker M of the movable element which is moved until it is put into an unlocked state.