To provide a fluorinated polymer which enables to reduce the amount of residual ink on partition walls and to form an ink layer having high uniformity in film thickness, and a negative photosensitive composition.A fluorinated polymer which is a copolymer made of at least two monomers each having an ethylenic double bond, and which has a side chain having a C20 or lower alkyl group in which at least one of its hydrogen atoms is substituted by a fluorine atom (provided that the alkyl group may contain an etheric oxygen atom between carbon atoms) and a side chain having at least two ethylenic double bonds per side chain.