We found that microwave induced discharge or microwave plasma could be easily produced with a perovskite-type oxide substrate even at atmospheric pressure. We investigated the plasma conditions in order to understand the plasma generation mechanism. When pressure in the reactor was gradually increased, the plasma mode was changed from a diffused glow to a filamentary glow at a power of about 5.3 x 10(4) Pa. The electron density of the plasma produced using a substrate was higher than that of the ordinary microwave plasma produced without the substrate. It was considered that the electron emissions from the substrate enhanced the plasma.