A new production technique of sheet‐shaped plasma by means of electron cyclotron resonance heating (ECRH) is proposed. The sheet plasma is produced in a vessel with rectangular cross section set in a rectangular magnetic field coil. The maximum density and electron temperature of the sheet plasma are about 2.6×1011cm−3and 7 eV, respectively, in a typical argon gas pressure ofP0=5×10−4Torr. The sheet plasma has several peaks of the density profile across the plasma width. These modes appear according to the change of working gas pressure. Those parameters including plasma density, density profile, and ion energy are controllable. This plasma is expected to be useful for material processing or plasma‐based high‐energy particle accelerators.