A mobile electronic device comprises an RFID antenna section that sends and receives signals on a first useful frequency band, a main antenna section that sends and receives signals on a second useful frequency band, which is a higher frequency band than the first useful frequency band, an adjustment section that adjusts a resonance frequency of the RFID antenna section, and a control section that identifies a reactance value of the RFID antenna section based on the receiving sensitivity with respect to signals on the first useful frequency band and adjusts the resonance frequency of the RFID antenna section based on the identified reactance value by an adjustment section such that a high-order resonance frequency of the RFID antenna section is spaced apart from the second useful frequency band.