A multiband antenna comprising a slot antenna and a radiation element, wherein: the slot antenna has a conductive plate; the conductive plate is formed with an opening portion and a slot; the slot partially opens through the opening portion; the slot extends long in a first direction; the radiation element has a first portion and a second portion; the first portion extends from the conductive plate toward an orientation away from the slot in a second direction perpendicular to the first direction; the first portion has a first length in the second direction; the second portion extends in the first direction from the first portion; the second portion has a second length in the first direction; the second length is greater than the first length; the opening portion connects the slot with an outside of the conductive plate in the second direction; and the opening portion is positioned between the radiation element and the slot in the second direction, characterized in that the slot includes a first slot and a second slot; the first slot and the second slot are positioned so that the opening portion is put between the first slot and the second slot in the first direction; the slot antenna comprises a feed point; the feed point is connected with the conductive plate across the first slot; the multiband antenna further comprises a first stub which is provided to correspond to the first slot; the conductive plate has a first connecting portion and a first opposed portion; the first connecting portion and the first opposed portion are positioned so that the first slot is put between the first connecting portion and the first opposed portion in the second direction; the first stub has a first end and a second end in the second direction; the first end of the first stub is connected with the first connecting portion; and the second end of the first stub is positioned away from the first opposed portion and faces the first opposed portion. the slot antenna has a conductive plate; the conductive plate is formed with an opening portion and a slot; the slot partially opens through the opening portion; the slot extends long in a first direction; the radiation element has a first portion and a second portion; the first portion extends from the conductive plate toward an orientation away from the slot in a second direction perpendicular to the first direction; the first portion has a first length in the second direction; the second portion extends in the first direction from the first portion; the second portion has a second length in the first direction; the second length is greater than the first length; the opening portion connects the slot with an outside of the conductive plate in the second direction; and the opening portion is positioned between the radiation element and the slot in the second direction, characterized in that the slot includes a first slot and a second slot; the first slot and the second slot are positioned so that the opening portion is put between the first slot and the second slot in the first direction; the slot antenna comprises a feed point; the feed point is connected with the conductive plate across the first slot; the multiband antenna further comprises a first stub which is provided to correspond to the first slot; the conductive plate has a first connecting portion and a first opposed portion; the first connecting portion and the first opposed portion are positioned so that the first slot is put between the first connecting portion and the first opposed portion in the second direction; the first stub has a first end and a second end in the second direction; the first end of the first stub is connected with the first connecting portion; and the second end of the first stub is positioned away from the first opposed portion and faces the first opposed portion.