An electrostatic capacitive sensor includes a plurality of transmitter electrodes, a plurality of receiver electrodes, and a control circuit. The control circuit includes: a transmitter circuit configured to apply a periodical transmission signal to each of the plurality of transmitter electrodes; and a receiver circuit configured to generate, based on a reception signal generated in each of the plurality of receiver electrodes in response to the transmission signal, a detection signal indicating a change in electrostatic capacitance formed at each of intersections of the plurality of transmitter electrodes and the plurality of receiver electrodes, wherein the transmitter circuit and the receiver circuit are configured to switch between a first mode and a second mode, in the first mode, the transmission/reception signal is sequentially applied/monitored and in the second mode, the plurality of transmitter/receiver electrodes are grouped so that the same signal is applied to the same group.