According to one embodiment, a sheet binding device includes a tape support base, a slide base, a tape holder, a first displacement mechanism, and a second displacement mechanism. The tape support base supports a tape. The slide base is movable in a first direction. The tape holder is supported on the slide base and is movable in a second direction crossing the first direction. The first displacement mechanism displaces the tape holder in a second direction from a first position that is a position away from the tape to a second position at which the tape holder is capable of coming into contact with the tape. The second displacement mechanism displaces the tape holder in the second direction from the second position to the first position.