A self-capacitance-system electrostatic-capacitance detection sensor includes: a first electrode and a second electrode, one of the first and second electrodes being set as a sense electrode, and the other of the first and second electrodes being set as a drive electrode; a sense-signal generating unit that generates a sense signal to be applied to the sense electrode; a detecting unit that detects, as a detection value, an amount of charge movement corresponding to an electrostatic capacitance of the sense electrode; and a determining unit that determines whether or not a detection target is in close proximity to both the first and second electrodes, based on a subtraction difference between detection values detected by the detecting unit when a first drive signal is applied to the drive electrode and when a second drive signal having the same frequency and a different phase is applied to the drive electrode.