Providing a water treatment system with which it is possible to efficiently share a plurality of water utilization means including a shower, and with which it is possible to use drain water in environments in which it is difficult to secure water. The water treatment system containing shower stalls which, when input water is used by a user, output the used water as drain water, wherein treated water sensors are capable of detecting a given physical amount, or an amount based thereon, pertaining to at least a portion among the water input to each information processing device controlling the shower stalls and the drain water output from each of the shower stalls. An information generation unit generates information pertaining to the use by a user of each of the shower stalls based on at least a portion of the results from the treated water sensors.