Abstract: A method for forming a waterproof film includes: providing a main component container that contains a main component for forming a waterproof film and discharges the main component as a piston is pushed, and a curing agent container that contains a curing agent for the main component and discharges the curing agent as a piston is pushed, the containers being encased in a pair of retainer cases arranged in a parallel arrangement, respectively; pushing the pistons for the main component container and the curing agent container in a synchronized manner by a single, compressed air-driven cylinder device that is arranged adjacent to the pair of retainer cases; through respective supply hoses, feeding the discharged main component and the curing agent to a spouting gun module that is held by an operator and supplied with compressed air; mixing the main component and the curing agent in a static mixer unit in the spouting gun module; and blowing the mixture with the flow of compressed air onto an object to be waterp