1. A zoom lens comprising, in order from an object side to an image side:a first lens unit having a positive refractive power;

a second lens unit having a negative refractive power; and

a third lens unit having a positive refractive power,

wherein the second lens unit is configured to move toward the image side during zooming from a wide angle end to a telephoto end, and an interval between adjacent lens units is changed during zooming,

wherein the first lens unit comprises a lens pair (LB1) of a positive lens (LP1) and a negative lens (LN1) that are arranged adjacent to each other, and a lens pair (LB2) of a positive lens (LP2) and a negative lens (LN2) that are arranged adjacent to each other,

wherein the second lens unit comprises a lens pair (LB3) of a positive lens (LP3) and a negative lens (LN3) that are arranged adjacent to each other, and

wherein the following conditional expressions are satisfied:

0.000<(?IRP1??IRN1)/(?IRP1??IRN1)<0.015;

?0.015<(?IRP2??IRN2)/(?IRP2??IRN2)<0.000; and

?0.005<(?IRP3??IRN3)/(?IRP3??IRN3)<0.015,

where, when a refractive index of a material at a wavelength of 400 nm is N400, a refractive index of the material at a wavelength of 1,050 nm is N1050, a refractive index of the material at a wavelength of 1,700 nm is N1700, an Abbe number ?IR of the material and a partial dispersion ratio ?IR of the material are ?IR=(N1050?1)/(N400?N1700) and ?IR=(N400?N1050)/(N400?N1700), respectively, ?IRP1 and ?IRP1 represent an Abbe number ?IR and a partial dispersion ratio ?IR of a first material for the positive lens (LP1), respectively, ?IRN1 and ?IRN1 represent an Abbe number ?IR and a partial dispersion ratio ?IR of a second material for the negative lens (LN1), respectively, ?IRP2 and ?IRP2 represent an Abbe number ?IR and a partial dispersion ratio ?IR of a third material for the positive lens (LP2), respectively, ?IRN2 and ?IRN2 represent an Abbe number ?IR and a partial dispersion ratio ?IR of a fourth material for the negative lens (LN2), respectively, ?IRP3 and ?IRP3 represent an Abbe number ?IR and a partial dispersion ratio ?IR of a fifth material for the positive lens (LP3), respectively, and ?IRN3 and ?IRN3 represent an Abbe number ?IR and a partial dispersion ration ?IR of a sixth material for the negative lens (LN3), respectively.