A method for producing a semiconductor layer containing a metal oxide, which comprises: coating an ink containing a metal salt of unsaturated carboxylic acid represented by the formula (I) on a base material; and conducting a heat treatment after the coating (In the formula (I), R 1 , R 2 and R 3 are each independently hydrogen atom or an arbitrary substituent, M is an m-valent metal atom, and m is an integer of 2 to 5, and m "CR 1 R 2 =CR 3 -COO - "s may be the same as or different from each other).