A water treatment device, comprising: a water tank which stores water; an insulating divider which divides a space inside the water tank into two treatment vessels (37, 38) adjacent to each other in a horizontal direction, and includes a current carrier (35, 81) which is able to energize water in the two treatment vessels (37, 38); a treatment unit (60, 80) including a pair of electrodes (61, 62) arranged one each in each of the treatment vessels (37, 38), a power supply which applies a voltage to the pair of electrodes (61, 62), and a power supply controller which switches between an ON operation of keeping the power supply ON and an OFF operation of turning the power supply OFF; a water supplier which supplies water to each of the treatment vessels (37, 38); and a draining member which drains water from each of the treatment vessels (37, 38), characterized in that: the treatment unit (60, 80) further includes a detector which detects a level of water in each of the treatment vessels (37, 38) based on an index corresponding to a current value between the pair of electrodes (61, 62), the current carrier is comprised of a small hole which is formed in the insulating divider to allow the two treatment vessels (37, 38) to communicate with each other, the treatment unit is comprised of a discharge unit which causes discharge inside the small hole, and a lower end of each of the pair of electrodes (61, 62) is at a level higher than an upper end of the small hole. a water tank which stores water; an insulating divider which divides a space inside the water tank into two treatment vessels (37, 38) adjacent to each other in a horizontal direction, and includes a current carrier (35, 81) which is able to energize water in the two treatment vessels (37, 38); a treatment unit (60, 80) including a pair of electrodes (61, 62) arranged one each in each of the treatment vessels (37, 38), a power supply which applies a voltage to the pair of electrodes (61, 62), and a power supply controller which switches between an ON operation of keeping the power supply ON and an OFF operation of turning the power supply OFF; a water supplier which supplies water to each of the treatment vessels (37, 38); and a draining member which drains water from each of the treatment vessels (37, 38), characterized in that: the treatment unit (60, 80) further includes a detector which detects a level of water in each of the treatment vessels (37, 38) based on an index corresponding to a current value between the pair of electrodes (61, 62), the current carrier is comprised of a small hole which is formed in the insulating divider to allow the two treatment vessels (37, 38) to communicate with each other, the treatment unit is comprised of a discharge unit which causes discharge inside the small hole, and a lower end of each of the pair of electrodes (61, 62) is at a level higher than an upper end of the small hole. the treatment unit (60, 80) further includes a detector which detects a level of water in each of the treatment vessels (37, 38) based on an index corresponding to a current value between the pair of electrodes (61, 62), the current carrier is comprised of a small hole which is formed in the insulating divider to allow the two treatment vessels (37, 38) to communicate with each other, the treatment unit is comprised of a discharge unit which causes discharge inside the small hole, and a lower end of each of the pair of electrodes (61, 62) is at a level higher than an upper end of the small hole.