A method for manufacturing casings of composite hand dryers and the structure thereof includes the processes of severing a reproduced steel rough material to form a front casing, bending the front casing, fabricating a first side casing and a second side casing that have respectively a coupling portion, assembling one end of the front casing with the first side casing and assembling another end of the front casing with the second side casing to form a finished composite hand dryer casing. The method and structure can eliminate rusting and product strength problems. Fabrication process is simplified and production cost is lower.