A zoom lens suitable for a projection lens in an image projection apparatus, including a plurality of lens units, comprising: a first lens unit that is disposed closest to a magnification side in the plurality of lens units; and magnification-varying lens units that are disposed closer to a reduction side than the first lens unit and move for variation of magnification; wherein the first lens unit has a negative optical power and includes, in order from the magnification side, a first-A lens sub-unit having a negative optical power and a first-B lens sub-unit having a positive optical power, wherein the first lens unit is configured such that, for focusing from an infinite side to a close side, the first-B lens sub-unit moves toward the reduction side, a distance between the first-A and first-B lens sub-units increases, and: either also the first-A lens sub-unit moves toward the reduction side, or the first-A lens sub-unit is unmoved for focusing and the first-B lens sub-unit satisfies the following condition: - 2000 < f 1 ⁢ B / f 1 < - 1.0 where f 1B represents a focal length of the first-B lens sub-unit, and f 1 represents a focal length of the entire first lens unit; characterized in that the following condition is satisfied: - 30 < SF < - 0.2 where SF = (RR + RF)/(RR-RF) when RR and RF respectively represent curvature radii of a most-reduction side lens surface and a most-magnification side surface of the first-B lens sub-unit. a first lens unit that is disposed closest to a magnification side in the plurality of lens units; and magnification-varying lens units that are disposed closer to a reduction side than the first lens unit and move for variation of magnification; wherein the first lens unit has a negative optical power and includes, in order from the magnification side, a first-A lens sub-unit having a negative optical power and a first-B lens sub-unit having a positive optical power, wherein the first lens unit is configured such that, for focusing from an infinite side to a close side, the first-B lens sub-unit moves toward the reduction side, a distance between the first-A and first-B lens sub-units increases, and: either also the first-A lens sub-unit moves toward the reduction side, or the first-A lens sub-unit is unmoved for focusing and the first-B lens sub-unit satisfies the following condition: - 2000 < f 1 ⁢ B / f 1 < - 1.0 where f 1B represents a focal length of the first-B lens sub-unit, and f 1 represents a focal length of the entire first lens unit; characterized in that the following condition is satisfied: - 30 < SF < - 0.2 where SF = (RR + RF)/(RR-RF) when RR and RF respectively represent curvature radii of a most-reduction side lens surface and a most-magnification side surface of the first-B lens sub-unit. either also the first-A lens sub-unit moves toward the reduction side, or the first-A lens sub-unit is unmoved for focusing and the first-B lens sub-unit satisfies the following condition: - 2000 < f 1 ⁢ B / f 1 < - 1.0 where f 1B represents a focal length of the first-B lens sub-unit, and f 1 represents a focal length of the entire first lens unit; characterized in that the following condition is satisfied: - 30 < SF < - 0.2 where SF = (RR + RF)/(RR-RF) when RR and RF respectively represent curvature radii of a most-reduction side lens surface and a most-magnification side surface of the first-B lens sub-unit.