PURPOSE: To provide a steam type retarder capable of decreasing its receiving space by attempting the size reduction of an air-liquid converter as well as improving its reliability by stably obtaining its operation as the result of prevention of blockage of an operation liquid port by means of a flexible film.

CONSTITUTION: An air-liquid converter 25 connected to an operational liquid flow passage 21 which provides connection between the operational liquid entrance 11a and the exit 11b of a steam type retarder 11 and makes increase/ decrease adjustment of the internal pressure of the stream type retarder 11 is subjected to partitioning of the inside of its air-liquid converter main body 25a inn an upper side operational liquid chamber 25c and a lower side air chamber 25d by means of an easily deformable flexible film 25b and a projection part 25f capable partitioning an operational liquid passage for providing communication between the operational liquid chamber 25c and an operational liquid port 25g is interposed between the flexible film 25b and the air-liquid converter main body 25a and around the operational liquid port 25g connected to the operational liquid flow passage 21.