Abstract: A multi-stage type flow rate switching device is provided which simplifies switching of flow paths and which rarely causes erroneous operation. The multi-stage type flow rate switching device includes a constant flow rate path 2 and a variable flow rate path 3 arranged in parallel between a liquid medicine flow inlet port 1 and a liquid medicine flow outlet port 4 where the variable flow rate path 3 can change the flow rate by means of a three-way stopcock 33. Although the flow rate can be switched in four stages when one variable flow rate path 3 is arranged as shown by FIG. 1, the flow rate can be switched in further multi-stages by providing two or more of the variable flow rate paths 3.

Abstract: A three-way stopcock and a flow rate control device having a flow rate control unit for controlling the flow rate by flow resistances of flow rate control tubes. The three-way stopcock includes a plug portion in a cylindrical shape having a liquid path in a T-like shape, a cylindrical portion having two flow inlet ports and one flow outlet port, into which the plug portion can be inserted rotatably and in a liquid tight fit, and a switch lever capable of attachably and detachably engaging with the plug portion, wherein when the liquid path of the plug portion communicates with the flow outlet portion of the cylindrical portion by rotation of the plug portion by the switching lever, the liquid path of the plug portion communicates with at least one of the two flow inlet ports of the cylindrical portion.