PURPOSE: To provide a cheap and high durable solar energy water heater by a method wherein vinyl hot water pipes are arranged in a heat accumulation box and a heat packing plate having U-shaped groove therein is fixed to the pipes.

CONSTITUTION: A number of vinyl hot water pipes 12 are arranged side-by-side in a heat accumulating box 8 where its bottom plate is of a heat-insulative plate 7 and its top plate is of a metallic heat-receiving plate 4, then its upper surface is covered by a transparent vinyl corrugated plate 5. The pipes are communicated with vinyl lateral frame pipes 10, 11 and the lateral frame pipe 11 is connected to an ascending flow pipe 15 in the double convection flow pipe 14 and the lateral frame pipe 10 is connected to the descending flow pipe 16 through a hot water pipe 12'. The hot water pipes 12, 12' are fitted in the U-shaped grooves formed in the metallic heat packing plate 13.