The present invention provides an alkali-soluble resin with which a cured film having high extensibility, reduced stress, high adhesion to a metal, and high heat resistance can be obtained, and a photosensitive resin composition containing the alkali-soluble resin, and the present invention is an alkali-soluble resin (A) including a structure represented by a general formula (1) wherein X1 represents a divalent organic group having 2 to 100 carbon atoms, Y1 and Y2 each represent a divalent to hexavalent organic group having 2 to 100 carbon atoms, X2 represents a tetravalent organic group having 2 to 100 carbon atoms, p and q each represent an integer in a range of 0 to 4, and n1 and n2 each represent an integer in a range of 5 to 100,000, wherein (I) and (II) described below are satisfied: (I) an organic group having an aliphatic chain having 8 to 30 carbon atoms is contained as X1 of the general formula (1) at a content of 30 to 70 mol % based on 100 mol % of a total of X1 and X2, and (II) an organic group having a diphenyl ether structure is contained as Y1 of the general formula (1) at a content of 1 to 30 mol % based on 100 mol % of a total of Y1 and Y2.