A swimming timer including a fluid container, a fluid channel, a fluid sensor, a control circuit board and a display device. The fluid channel is connected to the fluid container and the fluid sensor, and the control circuit board is wired with the fluid sensor and the display device. The fluid container is installed and mounted on a side-wall of a swimming lane. When a swimmer starts, turns and stops, the fluid container will be touched and compressed forcing the fluid inside to flow into the fluid channel. The fluid sensor detects the fluid flow and generates electronic signals accordingly for the control circuit board and the built-in timing and stopwatch program to use as the input commands of start, lap and stop to compute the swimming time and the number of swimming laps. The display device is to show the results for the swimmer reference.