Flowing gases of hydrocarbon molecules were irradiated by tightly focused ns and fs laser, and the products were captured in hexane solution. In the case of ns laser irradiation, short polyynes up to C12H2 were produced efficiently from all the hydrocarbons, propane, hexane, octane, benzene, and toluene. The yields vary significantly among the products from different target molecules, extending beyond the effects of difference in the vapor pressures. With an aid of the visible emission spectra of the focused spot, polyyne forming reaction is discussed. In the case of fs laser irradiation of hexane, polyynes were produced efficiently much more than the ns-laser case, whereas for the toluene target, polyynes were not produced. Such a variation in the polyyne yield suggests there would be more suitable molecules for formation of polyynes, or any other carbon-rich materials, by gas-phase laser irradiation method.