An in-vivo information acquiring apparatus includes an information acquiring unit that acquires in-vivo information, a transmitting unit that transmits the in-vivo information to an outside of a living body, a power source that serves to supply power to the information acquiring unit and the transmitting unit, a power supply unit that is provided between the power source and at least one of the information acquiring unit and the transmitting unit so as to supply the power of the power source to at least one of the information acquiring unit and the transmitting unit, an external signal detecting unit that detects an external control signal supplied from outside and generates a control signal according to a detected state of the external control signal, a power supply controller that controls a power supply state of the power supply unit according to the control signal supplied from the external signal detecting unit, and a masking unit that masks the control signal supplied to the power supply controller by the external signal detecting unit for a predetermined time period.