Provided are a portable electronic device which accurately judges service life of a battery even when the battery is replaced, and a method for controlling such portable electronic device. A control block (48) is provided with a voltage measuring section (100), which is connected to a rechargeable battery (32) and measures a voltage value of the rechargeable battery (32); and a control section (101), which measures the voltage of the rechargeable battery (32) by means of the voltage measuring section (100) each time recharging of the rechargeable battery (32) is started and ended, and controls to store recharge count information specified based on the measured voltage value in a storage section (42). The control section (101) performs prescribed information updating, based on the recharge count information, in the case where the recharge count information is acquired by means of an information acquiring section (49) which acquires the recharge count information relating to the rechargeable battery (32) from the external.