The invention relates to a medicine applicator for local treatment of oral mucosa. The medicine applicator comprises a medicine applying head, a piston rod, a piston head, a sealing cover, a first one-way valve, a second one-way valve and a third one-way valve; the medicine applying head is provided with a piston cavity, a medicine storage cavity and a medicine outlet hole; the first one-way valvecommunicates with the medicine storage cavity and the piston cavity and is opened unidirectionally towards the piston cavity, the second one-way valve communicates with the piston cavity and the medicine outlet hole and is opened unidirectionally towards the medicine outlet hole, and the medicine outlet hole is arranged in one side of the medicine applying head; one end of the sealing cover is detachably connected with the medicine applying head and is in sealed connection with the medicine storage cavity, and the third one-way valve is arranged on the sealing cover and is opened unidirectionally towards the medicine storage cavity; and the piston head is arranged in the piston cavity, the position, corresponding to the piston cavity, of the sealing cover is provided with a piston rod hole, and the piston rod passes through the piston rod hole to be connected to the piston head. According to the medicine applicator, a medical worker or a patient can conveniently apply a medicine to oral mucosal lesions, and the medicine applicator is suitable for accurate positioning and administration of the surfaces with complex shapes of various parts of an oral cavity, avoids contact of the medicine by hands, is quick, simple and hygienic, and improves the medicine application efficiency and medication experience.