A manufacturing process for brassiere, and especially for a brassiere of front clasp type, comprises a step of left side forming, a step of right side forming, a step of rear piece forming, and a step of joining. Both left part and the right part of the brassiere are integrally formed with a bra cup, an edge piece, and a shoulder band by way of the plastics or the rubber being treated injection molding or vacuum forming respectively. A clasp device is provided to engage the bra cups with shoulder bands having engaging device for engaging the rear piece. Both ends of the rear piece are joined to both the edge pieces respectively.