PURPOSE: To carry out the decarbonylation reaction of an organic acid halide at a low cost in improved economicity, without using expensive platinum, etc., by using europium or neodymium which is an inexpensive and highly active rare earth element or their compounds as a catalyst.

CONSTITUTION: At least one kind of a substance selected from the metal of neodymium and europium and their compounds is used as a catalyst for the decarbonylation of an organic acid halide. The above metal and/or metal compound can be used as the catalyst as it is or in the form supported on a carrier. The organic acid halide used as the raw material is e.g. benzoyl chloride, phthaloyl chloride, acetyl chloride, phenylacetyl chloride, etc. The reaction can be carried out either in liquid phase or vapor phase under reduced pressure, normal pressure or positive pressure.