A solid-state image pickup apparatus comprising: a plurality of two-dimensionally arrayed unit pixels, each of the unit pixels including an optical-electrical conversion element configured to perform optical-electrical conversion of an incident light; a charge conversion element and an output terminal provided for each of a plurality of pixel groups, each pixel group including one or more of the unit pixels, the charge conversion element being configured to convert a signal charge optical-electrical converted by the optical-electrical conversion element of each of the unit pixels in the pixel group to voltage or current, and the output terminal being capable of outputting a noise signal that occurs at the time of resetting the charge conversion element and a signal-noise sum signal obtained by adding a signal that has occurred by optical-electrical conversion to the noise signal separately; a plurality of first transfer lines to which the output terminals of a plurality of the pixel groups are connected in common, the plurality of first transfer lines being capable of holding voltages based on signals outputted from the output terminals; a plurality of second transfer lines provided in parallel with the first transfer lines, the plurality of second transfer lines being capable of holding a voltage; inter-transfer-line capacitive elements connecting the second transfer lines and the first transfer lines; a reset switch configured to reset each of the second transfer lines to a reset voltage; a readout switch provided for each of the second transfer lines; and a third transfer line to which the second transfer lines are connected in parallel via the readout switches, respectively, wherein the first transfer lines are configured to be used as parasitic capacitances, the second transfer lines are configured to be reset to the reset voltage while a noise voltage corresponding to the signal-noise outputted to the output terminal is held in the parasitic capacitances of the first transfer lines, and the solid-state image pickup apparatus is configured to cause the signal-noise sum signal outputted from the unit pixels to the output terminals to be read out to the first transfer lines which are caused to be in a floating potential state, an electric potential of the second transfer lines to be changed by a difference between a signal-noise sum voltage corresponding to the signal-noise sum signal and the noise signal of the first transfer lines via the inter-transfer-line capacitive elements, and the difference to be read out from the second transfer lines to the third transfer lines while the readout switch is in an ON state. a plurality of two-dimensionally arrayed unit pixels, each of the unit pixels including an optical-electrical conversion element configured to perform optical-electrical conversion of an incident light; a charge conversion element and an output terminal provided for each of a plurality of pixel groups, each pixel group including one or more of the unit pixels, the charge conversion element being configured to convert a signal charge optical-electrical converted by the optical-electrical conversion element of each of the unit pixels in the pixel group to voltage or current, and the output terminal being capable of outputting a noise signal that occurs at the time of resetting the charge conversion element and a signal-noise sum signal obtained by adding a signal that has occurred by optical-electrical conversion to the noise signal separately; a plurality of first transfer lines to which the output terminals of a plurality of the pixel groups are connected in common, the plurality of first transfer lines being capable of holding voltages based on signals outputted from the output terminals; a plurality of second transfer lines provided in parallel with the first transfer lines, the plurality of second transfer lines being capable of holding a voltage; inter-transfer-line capacitive elements connecting the second transfer lines and the first transfer lines; a reset switch configured to reset each of the second transfer lines to a reset voltage; a readout switch provided for each of the second transfer lines; and a third transfer line to which the second transfer lines are connected in parallel via the readout switches, respectively, wherein the first transfer lines are configured to be used as parasitic capacitances, the second transfer lines are configured to be reset to the reset voltage while a noise voltage corresponding to the signal-noise outputted to the output terminal is held in the parasitic capacitances of the first transfer lines, and the solid-state image pickup apparatus is configured to cause the signal-noise sum signal outputted from the unit pixels to the output terminals to be read out to the first transfer lines which are caused to be in a floating potential state, an electric potential of the second transfer lines to be changed by a difference between a signal-noise sum voltage corresponding to the signal-noise sum signal and the noise signal of the first transfer lines via the inter-transfer-line capacitive elements, and the difference to be read out from the second transfer lines to the third transfer lines while the readout switch is in an ON state.