The disclosure provides a collimating lens, a projecting module, and a mobile phone. An object side of the collimating lens is defined as adjacent to a laser transmitter, an image side of the collimating lens is defined as adjacent to an object to be measured. Along an optical axis from the object side to the image side, the collimating lens sequentially includes a first lens, a second lens, a third lens and a stop. An object side surface of the first lens is convex, an object side surface of the second lens is concave surface, an object side surface of the third lens is convex, and an image side surface of the third lens is convex. The stop is positioned between the third lens and the object to be measured. The material of each of the first lens, the second lens, and the third lens is plastic.