To recognize an optical element even in the state where it is impossible to recognize the position of the optical element.

A motor-driven revolver control device is configured to read out the present address of a revolver (S1), determine whether the obtained present address is an unfixed address or not (S2), and when determining the present address as the unfixed address (YES at S2), read out an encoder value, then, recognize the presence of an observation optical path P1 in any of intermediate paths A to E. A rotation path from the revolver position (any position in the intermediate paths A to E) specified from the read encoder value to a target address (an objective lens address corresponding to a switch depressed by the operator) is retrieved (S4), and the revolver is controlled to rotate based on the retrieval result (S5).