The invention relates to a reactor (1) and a process for continuously preparing H2S by converting a reactant mixture which comprises essentially gaseous sulfur and hydrogen over a catalyst, comprising a sulfur melt (9) at least in a lower subregion (8) of the reactor (1), into which gaseous hydrogen is introduced. The catalyst is arranged in at least one U-shaped tube (21) which is partly in contact with the sulfur melt (9), the at least one U-shaped tube (21) having at least one entry orifice (23) on a limb (26) above the sulfur melt (9), through which the reactant mixture can enter the U-shaped tube (21) from a reactant region (10) of the reactor (1), having a flow path within the at least one U-shaped tube, along which the reactant mixture can be converted in a reaction region comprising the catalyst (22), and having at least one exit orifice (24) in another limb (27) through which a product can exit into a product region (7).