An optical scanning endoscope apparatus, includes: an irradiation fiber having an emitting end thereof oscillatably supported and irradiating light from a light source part onto an object； and a drive mechanism for driving the emitting end so as to cause light from the light source to be irradiated onto the object, in which the apparatus has a first irradiation mode as an imaging mode (corresponding to t1) for repeatedly scanning a desired region of the object with light from the light source and a second irradiation mode (corresponding to t4) for irradiating, between the temporally-adjacent scans in the first irradiation mode, a designated region selected from the desired region of the object, and provides, when the second irradiation mode is started, the drive mechanism with an offset signal (I0) for irradiating the designated region, and maintains the offset signal while repeating the irradiation in the second irradiation mode.
