Plasma producing method and apparatus wherein a plurality of high-frequency antennas are arranged in a plasma producing chamber, and a high-frequency power supplied from a high-frequency power supply device (including a power source, a phase controller and the like) is applied to a gas in the chamber from the antennas to produce inductively coupled plasma. At least some of the plurality of high-frequency antennas are arranged in a fashion of such parallel arrangement that the antennas successively neighbor to each other and each of the antennas is opposed to the neighboring antenna. The high-frequency power supply device controls a phase of a high-frequency voltage applied to each antenna, and thereby controls an electron temperature of the inductively coupled plasma.