Disclosed herein is a signal transmitting device including a multiplexing section configured to generate a B/R ch by alternately multiplexing image signals read from B pixels and R pixels among image signals read and input in units of a predetermined number of samples in each of the first line and the second line from said image pickup element in an active region corresponding to a C ch in HD-SDI together with start code of one of SAV and EAV, and generate a G ch by multiplexing, in order, image signals read from G pixels in an active region corresponding to a Y ch in HD-SDI together with said start code; and an 8B/10B encoder configured to output serial digital data converted by 8B/10B-encoding the active regions on the B/R ch and the G ch having data structures corresponding to said HD-SDI and an auxiliary data region including SAV, EAV, LN, and CRCC.