To provide a control circuit for an optical amplifier and an optical transmission device for preventing occurrence of a light surge independently of a fluctuation in an input optical level.

This invention aims at an optical amplifier 4 the input optical level of which is dynamically changed by placing an optical switch 2 at a pre- stage of a transmission path of an optical signal. Further, the optical amplifier 4 is provided with a control loop to make an output optical level constant using an output constant control section 7. Through the configuration above, a stimulated LD shut-down signal is given to the output constant control section 7 only for a period of τ1+τ2 including a point of time when a switching state of the optical switch 2 is changed synchronously with a switching control signal to control the switching state of the optical switch 2 so as to stop driving of the stimulated LD of the optical amplifier 4.