This research aimed to evaluate the erosion-corrosion resistance of lead-free copper alloys depending on the flow rate of the test solution using jet-in-slit tests. JIS CAC411 and JIS CAC804 were used as lead-free copper alloy specimens. JIS CAC703, JIS C3771, and JIS CAC406, which are conventional valve materials, and pure copper were also tested. The results were described as follows : In case of JIS CAC411 and JIS CAC406 which have higher Sn concentration than the other specimens, the damage depth by erosion-corrosion was smaller than those of the other copper alloy specimens, and hardly increased with increasing flow rate of test solution. In case of JIS CAC804, erosion-corrosion occurred around the center of the specimen, and the damage depth increased with increasing flow rate. However, the damage depth on the outside of the specimen was more or less independent of the flow rate except for 0 L·min-1. The damage depth of JIS C3771 on the outside of the specimen was almost independent of the flow rate in the same way as JIS CAC804, when the flow rate was lower. For both the JIS CAC703 and Cu specimens, the damage depth at the center and on the outside of the specimen severely increased with increasing flow rate.