An endoscope apparatus includes an apparatus main body having a housing with a concave portion formed in one surface, and an endoscope unit including a detachable connector portion in the concave portion, wherein, when the connector portion is mounted to the concave portion, the connector portion constitutes a part of the one surface. More preferably, a packing is provided in the housing or the connector portion that, when the connector portion is mounted to the housing, retains the mutual mating surfaces of the housing and the connector portion in a closely contacting state.