Provided is a phototherapy device which enables a sufficient amount of light to reach a deep tissue to achieve a satisfactory therapy while preventing the increase in the skin temperature of an affected part, and which can achieve a comfortable therapy. The present invention provides a phototherapy device comprising a sheet-like member having a first surface on which an affected part is to be arranged and a surface light source for emitting light toward the sheet-like member, wherein the first surface is formed in an uneven shape so as to provide multiple grooves. The phototherapy device can be used for, for example, the treatment of an affected part in a rheumatoid arthritis patient.
