A tag circuit connected to an antenna and a load, the tag circuit comprising: a control part which is configured to respond to a command extracted from a radio wave received by the antenna by controlling the load; and a rectifying part which is configured to generate DC power to be supplied to the load by converting a radio wave received by the antenna into DC power, the rectifying part being capable of changing power conversion characteristics of converting the radio wave into DC power to be supplied to the load, wherein, the rectifying part includes either a first rectifying part, a second rectifying part, or a third rectifying part; the first rectifying part includes: a multistage rectifier circuit in which N (≥ 2) -number of unit rectifier circuits are connected in multiple stages and which is configured so as to be capable to output power from a plurality of intermediate stages including a final stage; and the tag circuit characterized in that: the first rectifying part further includes: an output supply circuit which selectively supplies the load with an output of the multistage rectifier circuit; the second rectifying part includes: N (≥ 2) -number of rectifier circuits with mutually different power conversion characteristics; and an output supply circuit which is configured to selectively supply the load with outputs of the N-number of rectifier circuits; and the third rectifying part includes: a charge pump constituted by diodes and capacitors; a plurality of ON-resistance reducing elements which are connected in parallel to each diode of the charge pump and in which a switch and a diode are connected in series; and the control part is configured to change the power conversion characteristics of the rectifying part such that DC power supplied to the load from the rectifying part is maximum power. a control part which is configured to respond to a command extracted from a radio wave received by the antenna by controlling the load; and a rectifying part which is configured to generate DC power to be supplied to the load by converting a radio wave received by the antenna into DC power, the rectifying part being capable of changing power conversion characteristics of converting the radio wave into DC power to be supplied to the load, wherein, the rectifying part includes either a first rectifying part, a second rectifying part, or a third rectifying part; the first rectifying part includes: a multistage rectifier circuit in which N (≥ 2) -number of unit rectifier circuits are connected in multiple stages and which is configured so as to be capable to output power from a plurality of intermediate stages including a final stage; and the tag circuit characterized in that: the first rectifying part further includes: an output supply circuit which selectively supplies the load with an output of the multistage rectifier circuit; a multistage rectifier circuit in which N (≥ 2) -number of unit rectifier circuits are connected in multiple stages and which is configured so as to be capable to output power from a plurality of intermediate stages including a final stage; and the tag circuit characterized in that: the first rectifying part further includes: an output supply circuit which selectively supplies the load with an output of the multistage rectifier circuit; the second rectifying part includes: N (≥ 2) -number of rectifier circuits with mutually different power conversion characteristics; and an output supply circuit which is configured to selectively supply the load with outputs of the N-number of rectifier circuits; and N (≥ 2) -number of rectifier circuits with mutually different power conversion characteristics; and an output supply circuit which is configured to selectively supply the load with outputs of the N-number of rectifier circuits; and the third rectifying part includes: a charge pump constituted by diodes and capacitors; a plurality of ON-resistance reducing elements which are connected in parallel to each diode of the charge pump and in which a switch and a diode are connected in series; and a charge pump constituted by diodes and capacitors; a plurality of ON-resistance reducing elements which are connected in parallel to each diode of the charge pump and in which a switch and a diode are connected in series; and the control part is configured to change the power conversion characteristics of the rectifying part such that DC power supplied to the load from the rectifying part is maximum power.