Effect　of　porosity　on　the　oxidation　behavior　of　porous　SiC　was　investigated　at　oxygen　partial　pressures　of 20 kPa　and 1 kPa．Evolution　rate　of　gases　generated　during　oxidation　was　measured　using　quadrupole　mass spectrometer． 　Weight gain was observed after oxidation in every sample．Cristobalite was detected as oxidation product on the　surface　of　the　sample　after　oxidation． These　results　indicate　that　the　oxidation　behavior　of　porous　SiC　was passive　oxidation　forming　the　protective　film． In　the　case　of　oxidation　at　oxygen　partial　pressure　of 20 kPa，both weight　gain　and　amomt　of　gas　evolved　were　increased　with　increasing　apparent　porosity． On　the　other　hand，in　the　case　of　oxygen　partial　pressure　 of　1 kPa，weight　gain　and　amount　of　gas　evolved　were　nearly　constant values　in　spite　of　increasing　apparent　porosity．

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