An image-pickup apparatus including a detector comprising a detecting unit and a reading circuit, the detecting unit including pixels, each of which including a conversion element, the reading circuit which includes a connecting unit that is electrically connected to a signal wire transferring an electric signal and that electrically connects the signal wire to a node, and which performs a reading operation to output the electric signal from the pixel. A control unit controls an operation of the reading circuit, and a sensing unit senses the end of radiation irradiation based on an output of the reading circuit, which is acquired during the period of an accumulation operation of the detector. The control unit starts establishing the electrical connection between the signal wire and the node through the connecting unit based on the sensed irradiation end, and retains the electrical connection until the start of the reading operation.