PURPOSE: To shorten a curing time for a resin, by a method wherein, in a thermoplastic resin injection-molding machine, a resin path such as a sprue is narrowed by inserting the end of a shear pin thereinto to generate shearing heat, which is applied to the resin.

CONSTITUTION: A shear pin 1 is inserted into a resin flow path 4 consisting of a sprue 1 and a runner 2. The shear pin 5 is located so that it can freely move forwardly and backwardly through the operation of a gap-adjusting screw 8 and a width of an annular resin passage gap 11 can be freely adjusted. A resin poured through a nozzle 6 flows through the sprue 1 and runner 2 to be cured in a cavity 7. Meanwhile, the gap 11 is narrowed properly by means of the shear pin 5, and thereby the resin is heated at the narrowed portion by shearing heat to a temperature sufficiently high to allow the resin to be cured. Accordingly, the resin can be cured in a short time.