The invention discloses a water adding device capable of improving the uniformity of mortar, and in particular relates to a water adding device for improving the stirring uniformity of the mortar. The water adding device serving as an affiliate member of a mortar stirring machine can be widely applied to the field of on-site stirring of or lab researches on mortar and concrete. The water adding device capable of improving the uniformity of mortar comprises a water container, a stirring mechanism, a water flow control mechanism, an aqueous solution flow guide pipe and a multi-outlet aqueous solution adding mechanism, wherein the stirring mechanism is mounted on the water container; the bottom of the water container is connected with the aqueous solution flow guide pipe; the other end of the aqueous solution flow guide pipe is connected with the multi-outlet aqueous solution adding mechanism; the stirring mechanism consists of a micro motor, a conical gear transmission box and a stirring blade; the micro motor is mounted on the outer wall of the water container; a transmission shaft of the micro motor penetrates through the outer wall of the water container and is connected with the conical gear transmission box; the output end of the conical gear box is connected with the stirring blade; the stirring blade is positioned at the lower half part of the water container.