A flow rate controller for adjusting a flow rate of a shower facility, comprising: a pipe body, comprising a channel, a water supply opening and a water outlet opening, wherein the water supply opening is adapted to connect to a water supply pipe, and the water supply opening communicates with the water outlet opening through the channel; a control assembly, comprising a fixed member and a rotatable member, wherein the fixed member is fixedly positioned in the pipe body, and includes a first flow hole; the rotatable member is coaxially and rotatably connected to the pipe body, so that the rotatable member is rotatable relative to the pipe body, and the rotatable member includes a plurality of second flow holes and a plurality of adjusting positions, wherein the second flow holes have different hole sizes to each other, and each of the adjusting positions is respectively corresponding to the corresponding one of the second flow holes; when the rotatable member rotates to one of the adjusting positions, the corresponding second flow hole (222a, 222b, 222c or 222d) overlaps the first flow hole; characterised by an outer sleeve fitted around the rotatable member, wherein when the outer sleeve rotates, the outer sleeve drives the rotatable member to rotate; the rotatable member comprises a rib protruding from an outer surface of the rotatable member, the outer sleeve comprises a slot recessed into an inner surface of the outer sleeve; the rib is correspondingly fitted into the slot, so that the outer sleeve and the rotatable member rotate synchronously; the pipe body has a plurality of marks for respectively illustrating the flow rates of the flow rate controller, each of the adjusting positions is respectively corresponding to the corresponding one of the marks; when the rotatable member rotates to one of the adjusting positions, the rib stays to indicate the corresponding mark. a pipe body, comprising a channel, a water supply opening and a water outlet opening, wherein the water supply opening is adapted to connect to a water supply pipe, and the water supply opening communicates with the water outlet opening through the channel; a control assembly, comprising a fixed member and a rotatable member, wherein the fixed member is fixedly positioned in the pipe body, and includes a first flow hole; the rotatable member is coaxially and rotatably connected to the pipe body, so that the rotatable member is rotatable relative to the pipe body, and the rotatable member includes a plurality of second flow holes and a plurality of adjusting positions, wherein the second flow holes have different hole sizes to each other, and each of the adjusting positions is respectively corresponding to the corresponding one of the second flow holes; when the rotatable member rotates to one of the adjusting positions, the corresponding second flow hole (222a, 222b, 222c or 222d) overlaps the first flow hole; characterised by an outer sleeve fitted around the rotatable member, wherein when the outer sleeve rotates, the outer sleeve drives the rotatable member to rotate; the rotatable member comprises a rib protruding from an outer surface of the rotatable member, the outer sleeve comprises a slot recessed into an inner surface of the outer sleeve; the rib is correspondingly fitted into the slot, so that the outer sleeve and the rotatable member rotate synchronously; the pipe body has a plurality of marks for respectively illustrating the flow rates of the flow rate controller, each of the adjusting positions is respectively corresponding to the corresponding one of the marks; when the rotatable member rotates to one of the adjusting positions, the rib stays to indicate the corresponding mark.