There is provided a projection lens unit for a pico-projector which comprises a lens array, a color composition prism, a cover glass and an image panel, the projection lens unit characterized in that: the lens array includes 1st to 6th lenses sequentially arrayed from a screen on which an image is projected, the 1st lens includes a stop side formed on a 1st side of the 1st lens, the stop side stops the passage of light, to perform the function of a diaphragm aperture, light passing from the 1st lens to the 6th lens travels in only one direction of the lens sides based on the diaphragm aperture, and parts of the lens sides through which the light does not pass are cut so that the whole height of the lens array is reduced.