A spectroscope includes an emitting portion from where light is output, a dispersive element which is disposed on a side of the light emitting portion, to which the light is output, an incidence portion on which, light dispersed by the dispersive element is incident, and a temperature-compensating element which is disposed between the emitting portion and the incidence portion, and which is such that, an angle of incidence of the light dispersed on the incidence portion becomes almost constant with respect to a change in temperature in an operating temperature range. Moreover, the optical apparatus has such spectroscope in which temperature is compensated.