To provide configuration of a signal amplifier and an optical signal receiver using the same, enabling to solve a problem of waveform deterioration being produced by external noise, etc. in the signal amplifier of the optical signal receiver. The optical signal receiver includes a first master-slave level detector for detecting a DC level of a normal phase signal, and a second master-slave level detector for detecting a DC level of an inverse phase signal. By adding alternated signal components respectively, a differential signal transmission is enabled. Accordingly, using two master-slave level detector having mutually symmetric configurations and thus enabling differential transmission, there can be obtained a signal amplifier which can cope with various transient responses produced at the top of a burst cell and is sufficiently protected against the disturbance produced by external noises.