The invention relates to the technical field of paint applying equipment, and discloses a paint applying device and method for a steel structure. The paint applying device comprises a base, wherein a shell body is fixedly installed on one side of the top of the base, a partition plate is vertically arranged inside the shell body and divides the shell body into a
coating bin on the left side and a spraying bin on the right side, a spiral
auger is rotationally installed inside the
coating bin, the top end of the spiral
auger extends to the outer side of the shell body, a horizontal shaft is rotationally installed at the top of the shell body, a
cam is fixedly installed on the outer side of the horizontal shaft, the bottom of the outer side of the
cam is movably abutted against a moving plate, the top ends of springs are fixedly installed on the two sides of the bottom of the moving plate, the bottom ends of the springs are fixedly installed at the top of the shell body, first bevel gears are fixedly installed on the outer side of the horizontal shaft and the top end of the spiral
auger correspondingly, and the two first bevel gears mesh with each other. The paint applying device is reasonable in design, paint spraying, conveying and
air drying work of the steel structure can be synchronously carried out, and the paint spraying efficiency can be improved through operation of spray heads and a rotating rod.