Provided is a water treatment device configured to perform a deionization treatment for the water to be treated, and the water treatment device includes a pressing member, a treatment container configured to store the water to be treated, a first electrode and a second electrode accommodated in the treatment container, a separator arranged between the first electrode and the second electrode, and a pair of collectors, which are accommodated in the treatment container, and are configured to apply a voltage to the first electrode and the second electrode. The pressing member is configured to press the first electrode and the second electrode in the treatment container.