An object of the present invention is to provide a catalyst which, in the FT process, exhibits a high chain growth probability, and a high catalytic activity, can stably and smoothly promote the reaction, exhibits a high productivity of C.sub.5+, and can efficiently produce liquid hydrocarbons, and a process therefore. The invention relates to a hydrocarbon-producing catalyst obtainable by supporting a ruthenium compound on a support composed of a manganese oxide and an aluminum oxide, and which satisfies at least one of characteristics (1) and (2): (1) the catalyst being treated with an aqueous alkaline solution and subsequently subjected to calcination treatment in the air at 150 to 500.degree. C., (2) the aluminum oxide being an aluminum oxide wherein pore volume formed by pores having a pore diameter of 8 nm or more accounts for 50% or more of total pore volume.