PURPOSE: To carry out the selective hydrogenation of an acetylene compound and phenylacetylene in styrene, in liquid phase under atmospheric or pressurized condition, by using a catalyst containing palladium and a VIB-group metal or its salt and supported on alumina.

CONSTITUTION: Acetylene compounds and phenylacetylene existing as impurities in styrene useful as a raw material of plastics and other chemicals are selectively hydrogenated in liquid phase under atmospheric or pressurized condition, and removed. The selective hydrogenation of the impurities can be promoted, and the removal ratio can be increased by carrying out the reaction in the presence of a catalyst containing palladium and a IVB-metal or its salt (e.g. tin, lead or nitrage, acetate, etc. containing said metals as cation) and supported on alumina. In addition to the above effects, the hydrogenation of styrene can be suppressed and the loss of styrene caused by the side reaction can be minimized.