PURPOSE: To provide a water purification device of separation type which is of a simple design and capable of removing a deposit on a purification layer easily.

CONSTITUTION: In a water purification device consisting of purification layers 20a arranged in order of the grain diameter of a filter medium from the upstream to the downstream of a water flow path 10, and filtering contaminated water introduced from the inflow part of the water flow path 10, and discharging the filtered water from an outflow part, the bottom structure of purification layers 20a is composed of a filter medium holding member with through holes for holding filter media having various grain diameters, and a bottom plate 10a which can be closed and discharges a residual sludge into the water flow path 10 from each purification layer 20a after purification.