A stuffed cusp field with a torus ECR surface is obtained by adding a toroidal stuffer field onto a simple cusp field. Results of the production of ECR plasma in this field is described. With sweeping the stuffer current, Iis start to increase when the ECR surface forms closed torus, and reaches up several times of one without the stuffer current. Only in this closed case, X-rays (> 3 keV) are detected by NaI scintillator. These disappear when an obstacle is inserted inside ECR torus, suggesting that the ECR torus is of primary importance to produce and maintain energetic electrons. A peak density and temperature measured by a floating double probe reach up to ne ≃ 2 × 1012cm–3 and Te ≃ 25eV at a low Ar pressure of p ≃ 7.3 × 10–6Torr with the microwave power of 380W.