A zoom lens of a novel configuration suitable for a collapsible lens barrel is disclosed. More specifically, here is disclosed a zoom lens, comprising four lens units which are, in the order from an object side toward an image side, positive, negative, positive and positive in optical power, and performing zooming by varying distances between each lens units. In this zoom lens, the fourth lens unit has a positive lens element and a negative lens element, and satisfies the following conditional expression:

where n is the Abbe number of the negative lens element of the fourth lens unit, and p is the Abbe number of the positive lens element of the fourth lens unit.