A fusion splicer that can execute fusion splice and reinforcement preparations of optical fibers to be next subjected to reinforcement treatment efficiently at a proper timing by keeping track of the reinforcement treatment progress state to perform fusion splice and reinforcement treatment in parallel with each other is provided.A fusion splicer includes a fusion splicing device for butting optical fiber end parts against each other and fusing them and a reinforcement treatment device for reinforcing the optical fibers subjected to the fusion splice with a reinforcement sleeve covered thereon, and a display for monitoring the state of fusion splice comprises a display function of displaying the progress state of reinforcement treatment. The reinforcement treatment progress state is displayed as temperature rise, heat insulation, cooling information or is displayed as time information or temperature information. If the fusion splicer includes a plurality of reinforcement treatment devices that can be controlled independently, the progress state of each reinforcement treatment device is displayed.