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 adjacent to each other in a horizontal direction, and includes a current carrier which is able to energize water in the two treatment vessels ; a treatment unit including a pair of electrodes arranged one each in each of the treatment vessels , a power supply which applies a voltage to the pair of electrodes , 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 ; and a draining member which drains water from each of the treatment vessels , characterized in that : the treatment unit further includes a detector which detects a level of water in each of the treatment vessels based on an index corresponding to a current value between the pair of electrodes , the current carrier is comprised of a small hole which is formed in the insulating divider to allow the two treatment vessels 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 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 adjacent to each other in a horizontal direction, and includes a current carrier which is able to energize water in the two treatment vessels ; a treatment unit including a pair of electrodes arranged one each in each of the treatment vessels , a power supply which applies a voltage to the pair of electrodes , 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 ; and a draining member which drains water from each of the treatment vessels , characterized in that : the treatment unit further includes a detector which detects a level of water in each of the treatment vessels based on an index corresponding to a current value between the pair of electrodes , the current carrier is comprised of a small hole which is formed in the insulating divider to allow the two treatment vessels 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 is at a level higher than an upper end of the small hole . the treatment unit further includes a detector which detects a level of water in each of the treatment vessels based on an index corresponding to a current value between the pair of electrodes , the current carrier is comprised of a small hole which is formed in the insulating divider to allow the two treatment vessels 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 is at a level higher than an upper end of the small hole . <EOS>