A radar apparatus comprising: a transmitting array antenna; a receiving array antenna; a radar transmitter configured to transmit a radar signal through the transmitting array antenna; and a radar receiver configured to receive, through the receiving array antenna, a reflected-wave signal produced by the radar signal being reflected by a target, characterised in that the transmitting array antenna is composed of a first antenna group including a plurality of transmitting antennas arranged in a first direction and a second antenna group including at least one transmitting antenna placed in a position inside at least one pair of adjacent transmitting antennas of the first antenna group in the first direction and a position different from the first antenna group in a second direction orthogonal to the first direction, the receiving array antenna is composed of a third antenna group including a plurality of receiving antennas arranged in the first direction and a fourth antenna that is one receiving antenna placed in a position outside an end of the third antenna group in the first direction and a position different from the third antenna group in the second direction, an interelement spacing between the adjacent transmitting antennas in the first direction is a sum of an aperture length of the third antenna group and a spacing between the third antenna group and the fourth antenna in the first direction, an interelement spacing in the first direction between a receiving antenna of the third antenna group located at an end on a second side opposite to a first side close to the position in which the fourth antenna is placed and each of the other antennas of the third antenna group is identical to an interelement spacing in the first direction between a transmitting antenna of the adjacent transmitting antennas located on the same side as the first side and each of the transmitting antennas of the second antenna group, and in a case where the first antenna group and the third antenna group are identical in position in the second direction, a position of each of the transmitting antennas of the second antenna group in the second direction and a position of the fourth antenna in the second direction are different. a transmitting array antenna; a receiving array antenna; a radar transmitter configured to transmit a radar signal through the transmitting array antenna; and a radar receiver configured to receive, through the receiving array antenna, a reflected-wave signal produced by the radar signal being reflected by a target, characterised in that the transmitting array antenna is composed of a first antenna group including a plurality of transmitting antennas arranged in a first direction and a second antenna group including at least one transmitting antenna placed in a position inside at least one pair of adjacent transmitting antennas of the first antenna group in the first direction and a position different from the first antenna group in a second direction orthogonal to the first direction, the receiving array antenna is composed of a third antenna group including a plurality of receiving antennas arranged in the first direction and a fourth antenna that is one receiving antenna placed in a position outside an end of the third antenna group in the first direction and a position different from the third antenna group in the second direction, an interelement spacing between the adjacent transmitting antennas in the first direction is a sum of an aperture length of the third antenna group and a spacing between the third antenna group and the fourth antenna in the first direction, an interelement spacing in the first direction between a receiving antenna of the third antenna group located at an end on a second side opposite to a first side close to the position in which the fourth antenna is placed and each of the other antennas of the third antenna group is identical to an interelement spacing in the first direction between a transmitting antenna of the adjacent transmitting antennas located on the same side as the first side and each of the transmitting antennas of the second antenna group, and in a case where the first antenna group and the third antenna group are identical in position in the second direction, a position of each of the transmitting antennas of the second antenna group in the second direction and a position of the fourth antenna in the second direction are different.