The invention provides an onium salt and a composition which are appropriately usable in a resist composition for a lithography process, wherein two kinds of active energy rays including first activeenergy rays such as electron beams or extreme ultraviolet rays and second active energy rays such as UV are used, and which are highly sensitive and have excellent pattern characteristics such as LWR.According to the present invention, an onium salt represented by one formula selected from among general formula (1), general formula (2), general formula (11) and general formula (12) is provided.