PURPOSE: To obtain an opening tool for opening and treating the crack or incision of shell or animal, able to be easily inserted even by an inexperienced person, capable of uniformly keeping the force applied to claws, easily opening the crack, etc., and keeping the opened state, having light weight and excellent workability and producible at a low cost.

CONSTITUTION: The tool is composed of a pair of pieces A, B each having a claw 2 made of stainless steel and a holding part 3 and a grip 5 made of a resin. The pieces are pivotally combined together and forced with inside springs 6, 6a to keep the claws 2 in contacting state. The claw 2 may have a stopper 11 and an antislip part 10 or the tool may be further provided with a fixing pin 8 and a pin fixer 9 to keep the claws in opened state.