A multiband antenna (10, 10A-P) which is configured to be connected to a host conductor, wherein: the multiband antenna (10, 10A-P) has a conductor main portion, a first ground terminal (14, 14C) and a second ground terminal (16, 16C); the conductor main portion extends in a horizontal plane which is defined by a first direction and a second direction perpendicular to the first direction and is longer in the first direction than in the second direction; the conductor main portion has a first long edge and a second long edge at both ends thereof in the second direction, respectively; the conductor main portion is formed with a slot and an opening portion; the slot is longer in the first direction than in the second direction; the opening portion is provided in the first long edge and connects the slot with an outside of the conductor main portion; the first ground terminal (14, 14C) and the second ground terminal (16, 16C) extend from the second long edge; the multiband antenna (10, 10A-P) further has a feeding terminal (30, 30F); the conductor main portion has a first short edge and a second short edge at both ends thereof in the first direction, respectively; the slot includes a first slot section and a second slot section which are arranged in the first direction; the first slot section is nearer to the first short edge than to the second short edge in the first direction; the second slot section is nearer to the second short edge than to the first short edge in the first direction; the feeding terminal (30, 30F) is provided on a side of the first short edge in the first direction when viewed from the opening portion; the first ground terminal (14, 14C) is located on the side of the first short edge at least in part when viewed from the feeding terminal (30, 30F); the second ground terminal (16, 16C) is located on a side of the second short edge at least in part when viewed from the feeding terminal (30, 30F); and feeding for the multiband antenna is carried out so as to extend over the first slot section, the first ground terminal (14, 14C) and the second ground terminal (16, 16C) are configured to be connected to the host conductor, characterized in that the first ground terminal (14, 14C) extends so as to be contiguous to the first short edge at least in part. the multiband antenna (10, 10A-P) has a conductor main portion, a first ground terminal (14, 14C) and a second ground terminal (16, 16C); the conductor main portion extends in a horizontal plane which is defined by a first direction and a second direction perpendicular to the first direction and is longer in the first direction than in the second direction; the conductor main portion has a first long edge and a second long edge at both ends thereof in the second direction, respectively; the conductor main portion is formed with a slot and an opening portion; the slot is longer in the first direction than in the second direction; the opening portion is provided in the first long edge and connects the slot with an outside of the conductor main portion; the first ground terminal (14, 14C) and the second ground terminal (16, 16C) extend from the second long edge; the multiband antenna (10, 10A-P) further has a feeding terminal (30, 30F); the conductor main portion has a first short edge and a second short edge at both ends thereof in the first direction, respectively; the slot includes a first slot section and a second slot section which are arranged in the first direction; the first slot section is nearer to the first short edge than to the second short edge in the first direction; the second slot section is nearer to the second short edge than to the first short edge in the first direction; the feeding terminal (30, 30F) is provided on a side of the first short edge in the first direction when viewed from the opening portion; the first ground terminal (14, 14C) is located on the side of the first short edge at least in part when viewed from the feeding terminal (30, 30F); the second ground terminal (16, 16C) is located on a side of the second short edge at least in part when viewed from the feeding terminal (30, 30F); and feeding for the multiband antenna is carried out so as to extend over the first slot section, the first ground terminal (14, 14C) and the second ground terminal (16, 16C) are configured to be connected to the host conductor, characterized in that the first ground terminal (14, 14C) extends so as to be contiguous to the first short edge at least in part. the first ground terminal (14, 14C) and the second ground terminal (16, 16C) are configured to be connected to the host conductor, characterized in that the first ground terminal (14, 14C) extends so as to be contiguous to the first short edge at least in part.