An in-vivo information acquiring apparatus (2) includes an information acquiring unit (33,34) that acquires in-vivo information, a transmitting unit (31) that transmits the in-vivo information to an outside of a living body (1), a battery (40) that supplies power to the information acquiring unit (33, 34) and the transmitting unit (31), a power supply switch Q that is provided between the battery (40) and each of the information acquiring unit (33,34) and the transmitting unit (31) to control the supply of power, a switch (20), a 1/2 frequency dividing circuit (43), and a mask signal generator (23). The switch (20) detects a magnetic signal of the magnet (50), and generates a signal Vin according to the magnetic signal. The 1/2 frequency dividing circuit (43) controls the switching of the power supply switch Q according to the signal Vin from the switch (20). The mask signal generator (23) masks the signal Vin supplied to the 1/2 frequency dividing circuit (43) for a predetermined time period.
