To provide a horizontal underwater electric mixer that does not suck air in even when water level is low, does not allow an air pocket to arise in a guide ring even if it is lowered and installed in an agitation tank for maintenance or the like, can attain a sufficient jet-agitation effect without generating vibration, can secure a sufficient amount of sucked water, is cheap and easily operable, is compact and lightweight, and has an excellent cooling effect on its motor.

The horizontal underwater electric mixer is constructed in such a manner that a cylindrical guide ring 3 comprising a front end functioning as a water ejection port 4A of a circular hole and tilting downward in the direction of its suction side positioned on its rear end is disposed to surround the outer circumference of a propeller 2, only the upper rim of the rear end of the guide ring 3 is extended up to the rear part of its horizontal underwater motor 1, the lower rim of the guide ring 3 is cut from the vicinity of the lower part of the front end of the horizontal underwater motor 1 in the obliquely upward and backward direction to form a tilting rim 5 facing downward, and an oval suction port 4B comprising the tilting rim 5 as the rim of its opening is opened from the vicinity of the lower part of the front end of the horizontal underwater motor 1 extending up to the rear part of the motor 1.