Electric power transmission device and electric power transmission system

An electric power transmission device as one aspect of the present invention comprises: a power transmitter that generates a magnetic field; a storage; and a power transmission controller. The storage stores a first parameter set concerning frequency hopping performed on a first frequency band and a second parameter set concerning frequency hopping performed on a second frequency band. The power transmission controller controls the power transmitter such that the frequency hopping is performed based on the parameter set acquired from the storage. The first frequency band is a band corresponding to a first resolution bandwidth for measuring a leakage magnetic field. The second frequency band is a band corresponding to a second resolution bandwidth intended for a higher band than the first resolution bandwidth.