To provide a reinforcing fitting for earthquake-proof slit and a stopper for reinforcing fitting, which easily attains firm connection of an earthquake-proof slit with a separator while reducing a construction time.

The reinforcing fitting for earthquake-proof slit comprises: a stopper to be engaged with a holding frame of the earthquake-proof slit; a clip to be engaged with the separator; and a connecting bar connecting the stopper with the clip, and firmly reinforces the earthquake-proof slit against placing pressure of concrete by engaging the clip installed to one end side of the connecting bar to be positionally adjustable with the separator, connecting the other end of the connecting bar to the stopper, engaging the stopper with the holding frame of the earthquake-proof slit, and transmitting the placing pressure of concrete to the earthquake-proof slit to the separator through the connecting bar by adjusting the installing position of the clip to the connecting bar. The stopper for reinforcing fitting includes a first claw to be engagingly locked with the holding frame and a second claw for preventing the dropping-out of the holding frame in an engagement part with the holding frame, and the stopper is engaged with the holding frame to reinforce the part between the engagement part and a connecting part by a reinforcement part to ensure the stopper strength and the earthquake-proof slit reinforcing strength.