A sulfonium salt used in a resist composition which gives a pattern having a high resolution, and small roughness in the photolithography using a high energy beam as a light source, and further difficultly eluted in water in the immersion lithography, and a resist composition containing the sulfonium salt, and a patterning process using the resist composition, wherein the sulfonium salt is represented by the following general formula (1a), wherein R represents a linear, branched, or cyclic monovalent hydrocarbon group having 1 to 30 carbon atoms at least one or more of the hydrogen atoms of which are substituted by a fluorine atom, R0 represents a hydrogen atom, or a linear, branched, or cyclic monovalent hydrocarbon group having 1 to 30 carbon atoms which may be substituted by a halogen atom, or interposed by a heteroatom.