A detector of liquid consumption condition includes first and second vibrating parts that can vibrate relatively to a containing space that can be filled and refilled with a liquid. At least a portion of the first and second vibrating parts are exposed to the containing space. Each of the vibrating parts are caused to vibrate by piezoelectric devices based on a driving signal and can generate a counter electromotive force signal by a vibration of the vibrating parts. A liquid consumption condition detecting part can detect a liquid consumption condition, based on the counter electromotive force signal from at least one of the piezoelectric devices. The containing space can contains a predetermined volume of the liquid, and the first vibrating part is placed near a surface of the liquid at a first level, and the second part is placed near a surface of the liquid at a second level.