An optical apparatus includes plural optical lens groups, an optical sensor, at least one lighting member and a casing. After a light beam passes through any of the plural optical lens groups, a travelling direction of the light beam is changed. After the light beam passes through at least one of the plural optical lens groups, the light beam is sensed and converted into an image signal by the optical sensor. The lighting member outputs a source beam. The plural optical lens groups, the optical sensor and the lighting member are accommodated within the casing. The optical apparatus has a single optical lens module, and is able to implement different optical functions simultaneously. Consequently, the overall volume of the optical apparatus is minimized, the fabricating cost of the optical apparatus is reduced, the assembling process is simplified, and the number of components to be assembled is reduced.