A micro-droplet generator comprises a main body, having a chamber accommodating liquid to be sprayed and a lateral opening, a spraying plate, placed in the opening and having a plurality of spraying holes as well as an inner side, a vibrating element, glued on the spraying plate and driving vibrations thereof, and a projection, placed inside the chamber and having an outer side touch with the inner side of the spraying plate, wherein a narrow space is left between the inner side of the spraying plate and the outer side of the projection, which upon the vibrations of the spraying plate has a varying width, upon becoming wider sucking in liquid from the chamber, and upon becoming narrower pressing out liquid through the spraying holes.