3-Difluoromethyl-1-methyl-1H-pyrazole-4-carboxylic acid and 3-trifluoromethyl-1-methyl-1H-pyrazole-4-carboxylic acid are useful intermediates for producing pyrazolylcarboxanilide fungicides (see, for example, Patent Documents 1 and 2). As a method of producing these intermediates, multiple methods are known (see, for example, Non-Patent Document 1). As a method of converting the substituent at the 4-position on the pyrazole ring to a carboxyl group to obtain a carboxylic acid, a method of oxidizing an aldehyde to a carboxylic acid is known (see, for example, Patent Document 3).