A new step‐and‐repeat x‐ray exposure system has been developed to establish practical submicron x‐ray lithography. Penumbra and run‐out error have been determined on the basis of resolution consideration and alignment accuracy analysis. The fundamental system parameters have been derived for constructing an efficient and accurate exposure system. To realize such a system, certain new technologies have been developed. (1) A high power Si–Kα x‐ray source brings a large x‐ray flux onto the wafer through a silicon nitride mask membrane. (2) The optical mark and gap detection method is connected to a precise alignment mechanism placed on anx–ytable designed for wafer stepping. (3) This construction ensures atmospheric environment exposure. (4) The exposure system operation is fully automatic thanks to microprocessors. A 0.5 μm pattern has been accurately replicated, and a ±0.15 μm alignment accuracy has been achieved using this exposure system.