The present invention discloses a zoom lens which reduces the size of an entire lens system, effectively corrects various types of aberration accompanying zooming and has good optical performance over the entire screen. The zoom lens comprises, in order from a front side to a rear side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, a fifth lens unit having a positive or negative refractive power and a sixth lens unit having a positive refractive power and satisfies the set forth conditions.