A catalyst used for a dehydrogenation reaction of at least one of formic acid and a formic acid salt, the catalyst being a salt of a complex: having a structure represented by any selected from the group consisting of the following Formulae, to: where R 1 to R 6 each independently denote an alkyl group, a hydroxy group (-OH), an alkoxy group (-OR), a nitro group, a halogen group, a carboxylic acid group, an alkylamino group, or a phenyl group, or adjacent R groups may be linked together to form a ring; and R 1 to R 6 may be substituted by one substituent or a plurality of substituents, Z 1 denotes a water molecule, a hydrogen atom, an alkoxide ion, a hydroxide ion, a halide ion other than a chloride ion, a carbonate ion, a trifluoromethanesulfonate ion, a sulfate ion, a nitrate ion, a formate ion, or an acetate ion, or is absent; and m denotes a positive integer, 0, or a negative integer, where R 7 to R 13 each independently denote a hydrogen atom, an alkyl group, a hydroxy group (-OH), an alkoxy group (-OR), a nitro group, a halogen group, a carboxylic acid group, an alkylamino group, or a phenyl group, or adjacent R groups may be linked together to form a ring; and R 7 to R 13 may be substituted by one substituent or a plurality of substituents, Z 2 denotes a water molecule, a hydrogen atom, an alkoxide ion, a hydroxide ion, a halide ion, a carbonate ion, a trifluoromethanesulfonate ion, a sulfate ion, a nitrate ion, a formate ion, or an acetate ion, or is absent; and n denotes a positive integer, 0, or a negative integer; provided that the complex is not having a structure selected from the group consisting of the following formulas to: R 1 to R 6 each independently denote an alkyl group, a hydroxy group (-OH), an alkoxy group (-OR), a nitro group, a halogen group, a carboxylic acid group, an alkylamino group, or a phenyl group, or adjacent R groups may be linked together to form a ring; and R 1 to R 6 may be substituted by one substituent or a plurality of substituents, Z 1 denotes a water molecule, a hydrogen atom, an alkoxide ion, a hydroxide ion, a halide ion other than a chloride ion, a carbonate ion, a trifluoromethanesulfonate ion, a sulfate ion, a nitrate ion, a formate ion, or an acetate ion, or is absent; and m denotes a positive integer, 0, or a negative integer, where R 7 to R 13 each independently denote a hydrogen atom, an alkyl group, a hydroxy group (-OH), an alkoxy group (-OR), a nitro group, a halogen group, a carboxylic acid group, an alkylamino group, or a phenyl group, or adjacent R groups may be linked together to form a ring; and R 7 to R 13 may be substituted by one substituent or a plurality of substituents, Z 2 denotes a water molecule, a hydrogen atom, an alkoxide ion, a hydroxide ion, a halide ion, a carbonate ion, a trifluoromethanesulfonate ion, a sulfate ion, a nitrate ion, a formate ion, or an acetate ion, or is absent; and n denotes a positive integer, 0, or a negative integer; provided that the complex is not having a structure selected from the group consisting of the following formulas to: R 7 to R 13 each independently denote a hydrogen atom, an alkyl group, a hydroxy group (-OH), an alkoxy group (-OR), a nitro group, a halogen group, a carboxylic acid group, an alkylamino group, or a phenyl group, or adjacent R groups may be linked together to form a ring; and R 7 to R 13 may be substituted by one substituent or a plurality of substituents, Z 2 denotes a water molecule, a hydrogen atom, an alkoxide ion, a hydroxide ion, a halide ion, a carbonate ion, a trifluoromethanesulfonate ion, a sulfate ion, a nitrate ion, a formate ion, or an acetate ion, or is absent; and n denotes a positive integer, 0, or a negative integer; provided that the complex is not having a structure selected from the group consisting of the following formulas to: