The present invention relates to a dental water heater. The water heater has a columnar body, and the body includes heating means extending in the axial direction of the body, and a plurality of layers of water channel sections arranged around the heating means. Each of the water channel sections spirally extends in the axial direction of the body. The adjacent pairs of the water channel sections are communicated either at upper or lower end portions thereof so as to together form a whole water channel. The whole water channel has an inlet and an outlet for water to be heated, so that water is supplied through the inlet, passed through the entire length of the whole water channel, and taken out as warmed water through the outlet.