Abstract: In a hot and cold water mixing device, the slope in a medium-temperature range is gently, and the slopes in a low-temperature range and a high-temperature range are steep. When the target temperature of water mixture is set in the medium-temperature range, a combined biasing force of serially-arranged bias springs acts on a main shaft leftwards, a biasing force of a temperature-sensitive spring acts on the main shaft rightwards, and these biasing forces balance with each other so that the main shaft and valve elements are stopped. When a handle is turned to enter into the high-temperature range exceeding, e.g. 50° C., a slide shaft biases the main shaft leftwards only with the second bias spring. When the handle is turned to enter into the low-temperature range, e.g. below 30° C., the slide shaft biases the main shaft only with the first bias spring leftwards.