A coupler for use in a liquid heater, comprising a male connector and a female socket connector configured to be coupled with the male connector, wherein: the male connector comprises a connecting wall and an annular cylindrical wall extending perpendicular to the connecting wall; the female socket connector comprises an end wall configured to be joined with the connecting wall of the male connector and a peripheral wall formed around the end wall and arranged perpendicularly to the end wall, wherein a surface of the end wall to be joined with the connecting wall is gradually lowered from a center towards a periphery and is convex-hull shaped, and the peripheral wall comprises arced sections and gapped sections connected between two arced sections, so that when the male connector is coupled with the female socket connector, the arced sections are allowed to be coupled with the annular cylindrical wall and no coupling is formed between the gapped sections and the annular cylindrical wall; the end wall is provided with a plurality of through holes, the peripheral wall forms a cavity, in which a second electric connector is disposed, a plurality of tubular divider walls is extended into the cavity in the axial direction from an undersurface of the end wall respectively at positions corresponding to the through holes; the connecting wall is provided with a mounting hole and a first electric connector mounted therein; and the first electric connector is to be in butt joint with the second electric connector through the through hole; characterized in that: a guide baffle is formed on the divider wall; the guide baffle extends obliquely; an undersurface of the guide baffle is disposed lower than an interior surface of the corresponding divider wall, so that water flowing from the end wall to the through hole can be led out along the guide baffle; and the guide baffle is located above the second electric connector. the male connector comprises a connecting wall and an annular cylindrical wall extending perpendicular to the connecting wall; the female socket connector comprises an end wall configured to be joined with the connecting wall of the male connector and a peripheral wall formed around the end wall and arranged perpendicularly to the end wall, wherein a surface of the end wall to be joined with the connecting wall is gradually lowered from a center towards a periphery and is convex-hull shaped, and the peripheral wall comprises arced sections and gapped sections connected between two arced sections, so that when the male connector is coupled with the female socket connector, the arced sections are allowed to be coupled with the annular cylindrical wall and no coupling is formed between the gapped sections and the annular cylindrical wall; the end wall is provided with a plurality of through holes, the peripheral wall forms a cavity, in which a second electric connector is disposed, a plurality of tubular divider walls is extended into the cavity in the axial direction from an undersurface of the end wall respectively at positions corresponding to the through holes; the connecting wall is provided with a mounting hole and a first electric connector mounted therein; and the first electric connector is to be in butt joint with the second electric connector through the through hole; characterized in that: a guide baffle is formed on the divider wall; the guide baffle extends obliquely; an undersurface of the guide baffle is disposed lower than an interior surface of the corresponding divider wall, so that water flowing from the end wall to the through hole can be led out along the guide baffle; and the guide baffle is located above the second electric connector. a guide baffle is formed on the divider wall; the guide baffle extends obliquely; an undersurface of the guide baffle is disposed lower than an interior surface of the corresponding divider wall, so that water flowing from the end wall to the through hole can be led out along the guide baffle; and the guide baffle is located above the second electric connector.