To provide a laser therapy device having a mechanism from which no laser beam is projected unless a laser beam output hole is covered with the skin.

A power jack 8 is connected to one end of a probe casing, and a plug 9 is inserted into an indoor wall outlet. The hand grip 5 of the probe casing is gripped to set a time switch 23 to bring the end 2 of the probe casing close to the affected part of the body of a patient. Then a main switch 7 is turned on to bring the end 2 of the probe casing into contact with the affected part. Through this contact, the inside of the probe casing is darkened, and a photodiode provided therein brings a laser drive circuit into operation on detecting a signal, thus emitting a laser beam.