An antenna apparatus including: a first antenna element (11, 11'); a second antenna element (12, 12'); and a branch circuit (13, 23, 33) to which the first antenna element (11, 11') and the second antenna element (12, 12') are coupled via respectively separate transmission lines (15, 16); wherein a delay process is conducted on one of the transmission lines (15, 16) by modifying the length (L1, L2) of the transmission line coupling the first antenna element (11, 11') to the branch circuit (13, 23, 33) or the transmission line coupling the second antenna element to the branch circuit (13, 23, 33), thereby adjusting the input impedance and/or phase of the first and second antenna elements (11, 11'; 12, 12') such that wider band characteristics (S2, C11) than the antenna characteristics of the first and second antenna elements (11, 11'; 12, 12') individually are configured, wherein a distance between the first antenna element (11, 11') and the second antenna element (12, 12') is taken to be an antenna-to-antenna distance, the antenna-to-antenna distance is set between a site where the absolute value of a current distribution of the first antenna element (11, 11') is maximized and another site where the absolute value of a current distribution of the second antenna element (12, 12') is maximized, the length of a delay line produced due to a difference in the lengths (L1, L2) of the two transmission lines (15, 16) is taken to be a delay line distance, an absolute value of the difference between the antenna-to-antenna distance and the delay line distance is made equal to an integer multiple, equal to or greater than 0, of the wavelength of a frequency at which transmitting or receiving is conducted in the antenna apparatus, and a sum of the antenna-to-antenna distance and the delay line distance is made equal to an integer multiple, equal to or greater than 1, of the wavelength of a center frequency at which transmitting or receiving is conducted in the antenna apparatus, wherein the branch circuit (23, 33) is configured as a hybrid circuit (23, 33) provided with two ports (21, 31; 22, 32) as ports coupled to a communication circuit, and received signals obtained at the two ports (21, 31; 22, 32) coupled to the communication circuit have diversity characteristics, wherein the hybrid circuit (23, 33) imparts a predetermined phase differential to a first frequency, the predetermined phase differential being 90° or 180°, wherein the hybrid circuit (23, 33) additionally imparts the predetermined phase differential to a second frequency. a first antenna element (11, 11'); a second antenna element (12, 12'); and a branch circuit (13, 23, 33) to which the first antenna element (11, 11') and the second antenna element (12, 12') are coupled via respectively separate transmission lines (15, 16); wherein a delay process is conducted on one of the transmission lines (15, 16) by modifying the length (L1, L2) of the transmission line coupling the first antenna element (11, 11') to the branch circuit (13, 23, 33) or the transmission line coupling the second antenna element to the branch circuit (13, 23, 33), thereby adjusting the input impedance and/or phase of the first and second antenna elements (11, 11'; 12, 12') such that wider band characteristics (S2, C11) than the antenna characteristics of the first and second antenna elements (11, 11'; 12, 12') individually are configured, wherein a distance between the first antenna element (11, 11') and the second antenna element (12, 12') is taken to be an antenna-to-antenna distance, the antenna-to-antenna distance is set between a site where the absolute value of a current distribution of the first antenna element (11, 11') is maximized and another site where the absolute value of a current distribution of the second antenna element (12, 12') is maximized, the length of a delay line produced due to a difference in the lengths (L1, L2) of the two transmission lines (15, 16) is taken to be a delay line distance, an absolute value of the difference between the antenna-to-antenna distance and the delay line distance is made equal to an integer multiple, equal to or greater than 0, of the wavelength of a frequency at which transmitting or receiving is conducted in the antenna apparatus, and a sum of the antenna-to-antenna distance and the delay line distance is made equal to an integer multiple, equal to or greater than 1, of the wavelength of a center frequency at which transmitting or receiving is conducted in the antenna apparatus, wherein the branch circuit (23, 33) is configured as a hybrid circuit (23, 33) provided with two ports (21, 31; 22, 32) as ports coupled to a communication circuit, and received signals obtained at the two ports (21, 31; 22, 32) coupled to the communication circuit have diversity characteristics, wherein the hybrid circuit (23, 33) imparts a predetermined phase differential to a first frequency, the predetermined phase differential being 90° or 180°, wherein the hybrid circuit (23, 33) additionally imparts the predetermined phase differential to a second frequency.