A photoconductive target having a transparent electrode (102) and a photoconductive layer (103) on a transparent substrate (101) is disposed opposite to a plurality of integrated electron emitters having electron emitters (106) and gate electrodes (104). A plurality of electron emitters applying electron beams to the photoconductive target are temporally changed over by an electron emitter selector circuit (107) and a gate selector circuit (108). Thereby, signal charge generated and stored in the photoconductive layer is read. A time-series electric signal corresponding to a spatial distribution of the incident light is generated. A thin imaging apparatus suitable for a larger area is thus provided.