It is possible to perform observation with easy viewing and a three-dimensional effect, when observing a wide-angle observation area. Provided is a three-dimensional-endoscope optical system 1 that is provided with two objective optical systems (2 and 3) having optical axes (2a and 3a), which are arranged with a spacing therebetween, and that satisfies the following conditions: 0.5 mm < OP < 1.5 mm 3 mm < D < 200 mm ± < 10 �¢ ° and 110 �¢ ° < É < 180 �¢ ° where OP is a spacing between the optical axes (2a and 3a) of optical members (4) at the most distal ends of the objective optical systems (2 and 3), D is a depth of field, ± is an angle of convergence (inward angle) of the depth of field D when performing near-point observation, and É is an angle of view of the objective optical systems (2 and 3).
