A first electronic device that wirelessly transmits power comprises: a power transmission circuit; a memory; a pulse generator; a foreign matter detection circuit that detects foreign matter located on a path for wirelessly transmitting power through the power transmission circuit; and a control circuit, wherein the control circuit may be configured to: wirelessly transmit power to a second electronic device on the basis of an AC input voltage applied to the power transmission circuit; generate a synchronized trigger signal at a first time point corresponding to a designated voltage of the input voltage through the pulse generator; store, in the memory, an output value of the foreign matter detection circuit identified at the first time point on the basis of the trigger signal; continue to acquire, from the memory, the output value stored in the memory for a specified time until a trigger signal of a next period is received by the memory from the pulse generator; and detect the foreign matter on the basis of the output value acquired during the specified time period.