A micro patch coating device includes a coating die with a micro channel structure. A coating fluid is supplied through a coating fluid inlet and an auxiliary fluid is supplied through an auxiliary fluid inlet. After a segment of a predetermined length of the coating fluid is formed at a two-phase fluid output section, the coating fluid flow is intercepted. In turn, a segment of predetermined length of the auxiliary fluid is formed at the two-phase fluid output section, and then the auxiliary fluid flow is intercepted. A two-phase fluid is formed and flows out of the coating die to the substrate to form micro patches thereon.