Provided is a power source switching circuit 100 of the present invention is a power source switching circuit for selectively connecting a first power source and a second power source where at least one of the first and second power sources is a battery power source to a load by switching the first power source and the second power source, the power source switching circuit includes: a first power source connection part and a second power source connection part configured to enable the connection of the first power source and the second power source thereto； a load connection part configured to enable the connection of the load thereto； a first switch part and a second switch part provided between each power source connection part and the load connection part； and a switching control part configured to perform a switch control of each switch part. Each switch part includes a plurality of FETs which are serially connected in the same direction such that a cathode side of a body diode is arranged on a load connection part side, and the number of plurality of FETs is the number which is determined such that a sum of forward drop voltages of the body diodes of each FET exceeds the difference between a full charge voltage and a discharge voltage of the battery power source. The power source switching circuit of the present invention can realize switching of power sources with high reliability.
