NOVELTY - Gas containing propylene and/or butene, ethylene and pentene is generated and separated to propylene-butene-containing material (a), ethylene-containing material (b) and pentene-containing material (c). Materials (b, c) are circulated to layer of olefin conversion catalyst (23a) to generate olefin shift-reaction gas. Material (a) and hydrogen are circulated to layer of olefin hydrogenation catalyst (24a) to obtain liquid petroleum gas.    USE - For manufacturing liquefied petroleum gas used as fuel for cassette stove, disposable lighter and motor vehicles.    ADVANTAGE - The method enables economical manufacture of liquefied petroleum gas, at high yield rate.    DETAILED DESCRIPTION - Source gas which contains methanol and/or dimethyl ether is circulated to catalyst layer which contains catalyst (21a) for olefin manufacture, and olefin-containing gas which contains propylene and/or butene as main components of olefin, and ethylene and pentene. The olefin-containing gas, and olefin shift-reaction generation gas obtained in an olefin conversion process are separated into propylene-butene-containing material, ethylene-containing material, and pentene-containing material. The ethylene-containing material and pentene-containing material are circulated to the catalyst layer which contains catalyst for olefin conversion. The olefin shift-reaction generation gas which contains propylene and/or butene is manufactured. The propylene-butene-containing material and hydrogen obtained in separation process are circulated to the catalyst layer which contains catalyst for olefin hydrogenation. Olefin hydrogenation is carried out to obtain the liquefied petroleum gas which contains hydrocarbon such as propane and/or butane.    DESCRIPTION OF DRAWING(S) - The figure shows the process-flow diagram of liquefied petroleum gas manufacturing apparatus.    reactor for olefin manufacture (21)    catalyst for olefin manufacture (21a)    splitters (22)    catalyst for olefin conversion (23a)    reactor for olefin hydrogenation (24)    catalyst for olefin hydrogenation (24a)