An antenna device includes: a first loop antenna including a first end portion and a second end portion that are fed, and having a first length corresponding to N times a wavelength at a communication frequency; a second loop antenna having a second length corresponding to N times the wavelength; a first connecting conductor configured to couple the first loop antenna and the second loop antenna to each other at a first position of a third length corresponding to M times a quarter wavelength at the communication frequency from the first end portion of the first loop antenna; and a second connecting conductor configured to couple the first loop antenna and the second loop antenna to each other at a second position of the third length from the second end portion of the first loop antenna and different from the first position.