A solid-state image pickup apparatus 1A includes a photodetecting section 10A and a signal readout section 20 etc. In the photodetecting section 10A, M×N pixel units P1,1 to PM,N are arrayed in M rows and N columns. When in a first imaging mode, a voltage value according to an amount of charges generated in a photodiode of each of the M×N pixel units in the photodetecting section 10A is output from the signal readout section 20. When in a second imaging mode, a voltage value according to an amount of charges generated in the photodiode of each pixel unit included in consecutive M1 rows in the photodetecting section 10A is output from the signal readout section 20. When in the second imaging mode than when in the first imaging mode, the readout pixel pitch in frame data is smaller, the frame rate is higher, and the gain being a ratio of an output voltage value to an input charge amount in the signal readout section 20 is greater.