The present invention relates to a medical device for preventing foot ulcer, which comprises : a foothold formed to be able to cover a foot sole of a user; a wearing member arranged at the foothold so that the user can wear the foothold; a light source member installed in the foothold and irradiating the foot of the user with light of a predetermined wavelength band in order to prevent foot ulcer on the foot of the user, wherein the foothold is flexible to be curved corresponding to the shape of the sole of the user. According to the present invention, the medical device for preventing foot ulcer is provided with the wearing member which can be worn on the sole of the user and has a flexible foothold to which the light source member is installed, to come into close contact with the sole, thereby enabling the user to move easily even during treatment.