The present invention provides a flow meter comprising a microprocessor that calculates an applied irrigation amount for a time period for an area of an irrigated site. In a state 1, the mobile station 21 checks a propagation line quality and instructs only the first base station 11 to transmit data to the mobile station 21. The light shielding part has liquid permeability and shields a background light traveling form the buffer, located on the opposite side of the bottom across the measurement object, toward the bottom of the container. The roofing filters may be off-chip inductancecapacitance filters.