PURPOSE: To reduce thickness of a solar battery-equipped small-type portable apparatus by using a small-capacity secondary battery, by a solar battery for charging the secondary battery having a 2-step voltage flattening section.

CONSTITUTION: A small-type portable apparatus is driven by a secondary battery 7 which is provided with two voltage-flattening sections including an early voltage flattening section ed, which can be used for approximately one month at a voltage of E2, and a voltage flattening section ab, which can be used for approximately one year at a voltage E1 being higher than E2, and equipped with a solar battery 1'. It is possible, by using this meachanism, to eliminate necessity of making the secondary battery capable of lasting two or three years, and therefore, the solar battery-equipped small-type portable apparatus can be made thinner.