We investigated the post-deposition heating (PDH) effect on OH content in SiOxfilms deposited by atmospheric-pressure CVD using a deposition source of silicone oil (SO) with O3and TCE vapor at a temperature Tdof 180 °C–250 °C. The PDH is performed in situ for 5 min in the deposition chamber just after film deposition without any supply of SO, where the heating temperature is the same as Td. The OH content in the films deposited normally decreases with increasing Td. In contrast, those with PDH decrease with deceasing Tdfrom 220 °C, and, at Td= 190 °C, a minimum OH content can be obtained. This means that lower OH content remains at a lower deposition temperature. The PDH effect on OH reduction can be explained by easily reconstructible structure of SiOxfilms deposited at low temperature. Furthermore, we discuss the mechanism of the PDH effect from other points of view.