The slide rail unit according to an exemplary of the invention includes an outer rail attachable to a rack, a middle rail slidably supported by the outer rail along the extending direction of the outer rail, and an inner rail slidably supported by the middle rail along the extending direction of the middle rail. The inner rail includes a lock mechanism. The lock mechanism includes a release member which releases a press against the middle rail by the inner rail when the inner rail slides in one direction along the extending direction of the middle rail, and a suppression member which prevents the middle rail from sliding in the one direction.