An electromagnetic coupler includes a first plane, a plurality of conductive patterns formed on the first plane and spaced apart from each other, a second plane parallel to the first plane, a ground pattern formed on the second plane and connected to ground, a first linear conductor formed to have a length shorter than ¼ a wavelength equivalent to a frequency used, the first linear conductor being connected at one end to one conductive pattern of the plural conductive patterns, and fed between an other end of the first linear conductor and the ground pattern, and a plurality of second linear conductors formed to have a length shorter than ¼ the wavelength equivalent to the frequency used, one or more of the second linear conductors being formed for each of the plural conductive patterns, to connect each of the plural conductive patterns and the ground pattern.