Microplasma has been studied with gaps from 10 to 1000 mum at near atmospheric pressure in a scanning electron microscope (SEM) chamber using CNTs for cathode. The field emission and gas discharge experiments were carried out at the same configuration. It was confirmed that field electron emission effectively provided primary electrons into the gap, which ignited discharge easily. In the case of gas discharge using carbon nanotubes for cathode, the cathode surface was not damaged even if the discharge current was more than 150 mA