A rotary atomizing head type coating machine comprising: a cylindrical housing (2, 31) whose inner peripheral side is a motor accommodating portion (4C, 32C); a cylindrical cover covering an outer peripheral side of said housing(2, 31); an air motor accommodated in said motor accommodating portion (4C, 32C) of said housing (2, 31) and rotating and driving a rotational shaft supported by an air bearing (6E, 6F) by a turbine; a rotary atomizing head located on the front side of said housing (2, 31) and mounted on a distal end portion of said rotational shaft of said air motor and spraying a paint supplied while rotating together with said rotational shaft; a feed tube provided by being inserted through said rotational shaft and supplying the paint toward said rotary atomizing head; a shaping air ring provided by surrounding an outer peripheral surface of said rotary atomizing head on the front end side of said housing (2, 31) and having an air ejection port for ejecting shaping air for shaping a spraying pattern of the paint sprayed from said rotary atomizing head; a bearing air passage provided on said housing (2, 31) and supplying bearing air toward said air bearing (6E, 6F) of said air motor; and a turbine air passage provided on said housing (2, 31) and supplying driving air toward said turbine of said air motor; and an annular space surrounding said air motor is provided between said housing (2, 31) and said cover; characterized in that: in said housing (2, 31), an air branch passage (18, 19) for connecting said bearing air passage and said annular space to each other and/or said turbine air passage and said annular space to each other and for leading a part of the compressed air into said annular space is provided; and said air branch passage (18, 19) has a narrower diameter than said air passage (13, 15), such that a part of the compressed air supplied from said bearing air passage and/or said turbine air passage toward said air motor is led into said annular space. a cylindrical housing (2, 31) whose inner peripheral side is a motor accommodating portion (4C, 32C); a cylindrical cover covering an outer peripheral side of said housing(2, 31); an air motor accommodated in said motor accommodating portion (4C, 32C) of said housing (2, 31) and rotating and driving a rotational shaft supported by an air bearing (6E, 6F) by a turbine; a rotary atomizing head located on the front side of said housing (2, 31) and mounted on a distal end portion of said rotational shaft of said air motor and spraying a paint supplied while rotating together with said rotational shaft; a feed tube provided by being inserted through said rotational shaft and supplying the paint toward said rotary atomizing head; a shaping air ring provided by surrounding an outer peripheral surface of said rotary atomizing head on the front end side of said housing (2, 31) and having an air ejection port for ejecting shaping air for shaping a spraying pattern of the paint sprayed from said rotary atomizing head; a bearing air passage provided on said housing (2, 31) and supplying bearing air toward said air bearing (6E, 6F) of said air motor; and a turbine air passage provided on said housing (2, 31) and supplying driving air toward said turbine of said air motor; and an annular space surrounding said air motor is provided between said housing (2, 31) and said cover; characterized in that: in said housing (2, 31), an air branch passage (18, 19) for connecting said bearing air passage and said annular space to each other and/or said turbine air passage and said annular space to each other and for leading a part of the compressed air into said annular space is provided; and said air branch passage (18, 19) has a narrower diameter than said air passage (13, 15), such that a part of the compressed air supplied from said bearing air passage and/or said turbine air passage toward said air motor is led into said annular space. in said housing (2, 31), an air branch passage (18, 19) for connecting said bearing air passage and said annular space to each other and/or said turbine air passage and said annular space to each other and for leading a part of the compressed air into said annular space is provided; and said air branch passage (18, 19) has a narrower diameter than said air passage (13, 15), such that a part of the compressed air supplied from said bearing air passage and/or said turbine air passage toward said air motor is led into said annular space.