A zoom lens comprising in order from an object side to an image side: a first lens unit having a positive refractive power and configured not to move for zooming; a second lens unit having a negative refractive power and configured to move to the image side for zooming from a wide angle end to a telephoto end; a third lens unit configured to move for zooming; and a relay lens unit having a positive refractive power and configured not to move for zooming, wherein the first lens unit consists of five or six lenses concluding, in order from the object side to the image side, with a negative lens, a positive lens, a positive lens, a positive lens and a positive lens, and conditional expressions 1.79 < Nn < 1.91, and 1.53 ≤ fn / f 1 < 2.0 are satisfied, where Nn represents a refractive index of the negative lens in the first lens unit, fn represents a focal length of the negative lens, and f1 represents a focal length of the first lens unit, characterized in that furthermore, the conditional expressions 39 < ν n < 48, and and 2.24 < Nn + 0.01 × ν n < 2.32 are satisfied, where vn represents an Abbe number of the negative lens, the Abbe number v being expressed by an expression ν = Nd − 1 / NF − NC where NF, Nd and NC represent refractive indices with respect to an F-line, a d-line and a C-line of Fraunhofer lines, respectively, and wherein said third lens unit has negative power, and wherein, either a) said first lens unit consists of six lenses, the lens closest to the object side is a positive lens, and said zoom lens comprises a negative fourth lens unit that moves for zooming and a positive fifth lens unit that moves for zooming, arranged in this order from the object side to the image side between said third lens unit and said relay lens; b) said first lens unit consists of six lenses, the lens closest to the object side is a positive lens, and said zoom lens comprises a positive fourth lens unit that moves for zooming and is arranged between said third lens unit and said relay lens; or c) said first lens unit consists of five lenses, and said zoom lens comprises a positive fourth lens unit which moves for zooming and is arranged between said third lens unit and said relay lens. a first lens unit having a positive refractive power and configured not to move for zooming; a second lens unit having a negative refractive power and configured to move to the image side for zooming from a wide angle end to a telephoto end; a third lens unit configured to move for zooming; and a relay lens unit having a positive refractive power and configured not to move for zooming, wherein the first lens unit consists of five or six lenses concluding, in order from the object side to the image side, with a negative lens, a positive lens, a positive lens, a positive lens and a positive lens, and conditional expressions 1.79 < Nn < 1.91, and 1.53 ≤ fn / f 1 < 2.0 are satisfied, where Nn represents a refractive index of the negative lens in the first lens unit, fn represents a focal length of the negative lens, and f1 represents a focal length of the first lens unit, characterized in that furthermore, the conditional expressions 39 < ν n < 48, and and 2.24 < Nn + 0.01 × ν n < 2.32 are satisfied, where vn represents an Abbe number of the negative lens, the Abbe number v being expressed by an expression ν = Nd − 1 / NF − NC where NF, Nd and NC represent refractive indices with respect to an F-line, a d-line and a C-line of Fraunhofer lines, respectively, and wherein said third lens unit has negative power, and wherein, either a) said first lens unit consists of six lenses, the lens closest to the object side is a positive lens, and said zoom lens comprises a negative fourth lens unit that moves for zooming and a positive fifth lens unit that moves for zooming, arranged in this order from the object side to the image side between said third lens unit and said relay lens; b) said first lens unit consists of six lenses, the lens closest to the object side is a positive lens, and said zoom lens comprises a positive fourth lens unit that moves for zooming and is arranged between said third lens unit and said relay lens; or c) said first lens unit consists of five lenses, and said zoom lens comprises a positive fourth lens unit which moves for zooming and is arranged between said third lens unit and said relay lens. a) said first lens unit consists of six lenses, the lens closest to the object side is a positive lens, and said zoom lens comprises a negative fourth lens unit that moves for zooming and a positive fifth lens unit that moves for zooming, arranged in this order from the object side to the image side between said third lens unit and said relay lens; b) said first lens unit consists of six lenses, the lens closest to the object side is a positive lens, and said zoom lens comprises a positive fourth lens unit that moves for zooming and is arranged between said third lens unit and said relay lens; or c) said first lens unit consists of five lenses, and said zoom lens comprises a positive fourth lens unit which moves for zooming and is arranged between said third lens unit and said relay lens.