A production technique for sheet plasma with a dc magnetron discharge source is proposed. The magnetron discharge was realized by a cross field of permanent magnets and a rectangular‐typed hollow cathode, which enhances the production of high‐density plasma. The plasma produced was introduced into a low‐pressure region where an axial magnetic field was applied through a slit anode to form the sheet plasma, of high electron density of 4.5×1010cm−3, electron temperature of 2.8 eV for low discharge current (0.3 A) and low magnetic field (0.18 kG). The thickness of the sheet plasma is found to be almost the same as the ion cyclotron diameter. This plasma production technique would be useful for thin‐film preparation on large‐area substrates.