To provide a method for simply producing a carboxylic acid from a chain state 1,2-diol.

This method for producing the carboxylic acid is characterized by performing a reaction of the chain state 1,2-diol with hydrogen peroxide in the presence of a metal oxide catalyst obtained by performing a reaction of hydrogen peroxide with at least 1 kind selected from a group consisting of tungsten metal, molybdenum metal, a tungsten compound consisting of the tungsten and an element of IIIb group, IVb group, Vb group or VIb group except for oxygen, and a molybdenum compound consisting of the molybdenum and an element of IIIb, IVb, Vb or VIb except for oxygen.