A heating/heat-retaining device, particularly to a heating/heat-retaining device used in the forging process, and more particularly to an opening-and-closing type heater and a wind generator shaft forging process using the same. The opening-and-closing type heater comprises a base, a tube body mounted on the base and a tube body opening-and-closing mechanism; the tube body comprises a fixed tube body and a movable tube body, the fixed tube body and the movable tube body are arc-shaped shells, and form a hollow shape when the openings thereof match with each other; the tube body opening-and-closing mechanism is connected to the movable tube body for realizing the opening-and-closing of the movable tube body and the fixed tube body. The invention solves heat retaining and heating problems during the forging process of the main shaft forgings and avoids internal defects due to rapid temperature drop of the main shaft forgings.