A power transmission device, comprising: a power transmission unit (202, 203) configured to perform wireless power transmission; a communication unit configured to perform wireless communication within a range wider than a power transmission possible range of the power transmission unit (202, 203); and a power transmission control circuit configured to control power of wireless power transmission of the power transmission unit (202, 203), wherein the power transmission control circuit is configured to: detect a first number of power reception devices for which the communication unit received a response indicating that power reception is performed from power reception devices receiving power equal to or more than a threshold from the power transmission device or another power transmission device when the power transmission unit (202, 203) performs power transmission by first power, and a second number of power reception devices for which the communication unit received a response indicating that power reception is performed from power reception devices receiving power equal to or more than the threshold from the other power transmission device when the power transmission unit (202, 203) does not perform power transmission or performs power transmission by second power smaller than the first power, determine a number of the power reception devices receiving power equal to or more than the threshold from the power transmission device by subtracting the second number of the power reception devices from the first number of the power reception devices, and control the power of wireless power transmission of the power transmission unit (202, 203) according to the number of the power reception devices receiving power equal to or more than the threshold from the power transmission device. a power transmission unit (202, 203) configured to perform wireless power transmission; a communication unit configured to perform wireless communication within a range wider than a power transmission possible range of the power transmission unit (202, 203); and a power transmission control circuit configured to control power of wireless power transmission of the power transmission unit (202, 203), wherein the power transmission control circuit is configured to: detect a first number of power reception devices for which the communication unit received a response indicating that power reception is performed from power reception devices receiving power equal to or more than a threshold from the power transmission device or another power transmission device when the power transmission unit (202, 203) performs power transmission by first power, and a second number of power reception devices for which the communication unit received a response indicating that power reception is performed from power reception devices receiving power equal to or more than the threshold from the other power transmission device when the power transmission unit (202, 203) does not perform power transmission or performs power transmission by second power smaller than the first power, determine a number of the power reception devices receiving power equal to or more than the threshold from the power transmission device by subtracting the second number of the power reception devices from the first number of the power reception devices, and control the power of wireless power transmission of the power transmission unit (202, 203) according to the number of the power reception devices receiving power equal to or more than the threshold from the power transmission device. detect a first number of power reception devices for which the communication unit received a response indicating that power reception is performed from power reception devices receiving power equal to or more than a threshold from the power transmission device or another power transmission device when the power transmission unit (202, 203) performs power transmission by first power, and a second number of power reception devices for which the communication unit received a response indicating that power reception is performed from power reception devices receiving power equal to or more than the threshold from the other power transmission device when the power transmission unit (202, 203) does not perform power transmission or performs power transmission by second power smaller than the first power, determine a number of the power reception devices receiving power equal to or more than the threshold from the power transmission device by subtracting the second number of the power reception devices from the first number of the power reception devices, and control the power of wireless power transmission of the power transmission unit (202, 203) according to the number of the power reception devices receiving power equal to or more than the threshold from the power transmission device.