A flow rate control device equipped with a housing, a flow passage disposed in an interior of the housing and through which a fluid can flow, a displacement member, which, by displacement thereof with respect to the flow passage, is capable of controlling a flow rate of the fluid that flows therethrough, and a flow rate adjustment indicating mechanism (12, 12A to 12F) that operates displacement of the displacement member; the flow rate adjustment indicating mechanism (12, 12A to 12F) comprising: a main body portion; a displacement operating member disposed rotatably with respect to the main body portion and connected to the displacement member, and which causes displacement of the displacement member by a rotating operation of the displacement operating member; and a rotating member, which is formed in an annular shape having a hole through which the displacement operating member is inserted, the rotating member being arranged in the main body portion such that a center of rotation of the rotating member is offset with respect to an insertion position of the displacement operating member, and the displacement operating member comprising an engagement part (122, 122A) that is engaged directly with the rotating member under rotation of the displacement operating member, wherein the rotating member has an indicating section by which a change in the flow rate of the fluid is indicated along a circumferential direction thereof, and the indicating section is displaced in the circumferential direction by engagement with the engagement part (122, 122A), whereby a position of the indicating section is changed, wherein plural inscribed teeth (176, 176A) are formed along a circumferential direction on an inner circumferential surface of the rotating member that constitutes the hole; and wherein on an outer circumferential surface of the displacement operating member, there are arranged side-by-side along a circumferential direction a meshing portion (122, 122A), which is capable of being enmeshed with a tooth gap between two adjacent teeth of the inscribed teeth (176, 176A) and serves as the engagement part (122, 122A), and an idling portion, which is not enmeshed with the inscribed teeth (176, 176A), characterized in that a rotation regulating mechanism (162, 162A to 162E), which is capable of regulating rotation of the rotating member in a condition in which the idling portion of the displacement operating member is arranged in confronting relation to the inscribed teeth (176, 176A), is disposed on the main body portion, and that the rotation regulating mechanism (162, 162A to 162E) is provided continuously within the main body portion, and comprises an elastic regulating member (162, 162A to 162E) that abuts against the inscribed teeth (176, 176A) and elastically presses the rotating member.. a main body portion; a displacement operating member disposed rotatably with respect to the main body portion and connected to the displacement member, and which causes displacement of the displacement member by a rotating operation of the displacement operating member; and a rotating member, which is formed in an annular shape having a hole through which the displacement operating member is inserted, the rotating member being arranged in the main body portion such that a center of rotation of the rotating member is offset with respect to an insertion position of the displacement operating member, and the displacement operating member comprising an engagement part (122, 122A) that is engaged directly with the rotating member under rotation of the displacement operating member, wherein the rotating member has an indicating section by which a change in the flow rate of the fluid is indicated along a circumferential direction thereof, and the indicating section is displaced in the circumferential direction by engagement with the engagement part (122, 122A), whereby a position of the indicating section is changed, wherein plural inscribed teeth (176, 176A) are formed along a circumferential direction on an inner circumferential surface of the rotating member that constitutes the hole; and wherein on an outer circumferential surface of the displacement operating member, there are arranged side-by-side along a circumferential direction a meshing portion (122, 122A), which is capable of being enmeshed with a tooth gap between two adjacent teeth of the inscribed teeth (176, 176A) and serves as the engagement part (122, 122A), and an idling portion, which is not enmeshed with the inscribed teeth (176, 176A), characterized in that a rotation regulating mechanism (162, 162A to 162E), which is capable of regulating rotation of the rotating member in a condition in which the idling portion of the displacement operating member is arranged in confronting relation to the inscribed teeth (176, 176A), is disposed on the main body portion, and that the rotation regulating mechanism (162, 162A to 162E) is provided continuously within the main body portion, and comprises an elastic regulating member (162, 162A to 162E) that abuts against the inscribed teeth (176, 176A) and elastically presses the rotating member..