An in-plane switching liquid crystal display comprising: a first polarizer plate; a second polarizer plate; and a liquid crystal cell, which is horizontally aligned and filled with liquid crystal of positive dielectric anisotropy (Δ ε>0) or negative dielectric anisotropy (Δε<0), an optical axis of the liquid crystal filled in the liquid crystal cell being aligned in-plane in parallel to the first and second polarizer plates (1, 2), wherein an absorption axis of the first polarizer plate is perpendicular to an absorption axis of the second polarizer plate, the optical axis of the liquid crystal filled in the liquid crystal cell is parallel to the absorption axis of the first polarizer plate, a positive biaxial retardation film (11; 13) defined by a following Equation is aligned between the liquid crystal cell and the second polarizer plate, an optical axis (12; 14) of the positive biaxial retardation film (11; 13) is perpendicular to the absorption axis of the second polarizer plate n x ≠ n y ≠ n z and n x > n y and n z > n y, wherein n x and n y are in-plane refractive indexes, n z is a thickness refractive index, and the positive biaxial retardation film (11; 13) has a positive in-plane retardation value (R in = d × (n x - n y)) and a positive thickness retardation value (R th = d × (n z - n y)) in which d is a thickness of a film, characterized in that an in-plane retardation value of the positive biaxial retardation film (11; 13) is equal to or less than 180nm at a wavelength of 550nm and that the positive biaxial retardation film (11; 13) has a normal wavelength dispersion or flat wavelength dispersion characteristic, and that the first polarizer plate and the second polarizer plate have internal protective films respectively. a first polarizer plate; a second polarizer plate; and a liquid crystal cell, which is horizontally aligned and filled with liquid crystal of positive dielectric anisotropy (Δ ε>0) or negative dielectric anisotropy (Δε<0), an optical axis of the liquid crystal filled in the liquid crystal cell being aligned in-plane in parallel to the first and second polarizer plates (1, 2), wherein an absorption axis of the first polarizer plate is perpendicular to an absorption axis of the second polarizer plate, the optical axis of the liquid crystal filled in the liquid crystal cell is parallel to the absorption axis of the first polarizer plate, a positive biaxial retardation film (11; 13) defined by a following Equation is aligned between the liquid crystal cell and the second polarizer plate, an optical axis (12; 14) of the positive biaxial retardation film (11; 13) is perpendicular to the absorption axis of the second polarizer plate n x ≠ n y ≠ n z and n x > n y and n z > n y, wherein n x and n y are in-plane refractive indexes, n z is a thickness refractive index, and the positive biaxial retardation film (11; 13) has a positive in-plane retardation value (R in = d × (n x - n y)) and a positive thickness retardation value (R th = d × (n z - n y)) in which d is a thickness of a film, characterized in that an in-plane retardation value of the positive biaxial retardation film (11; 13) is equal to or less than 180nm at a wavelength of 550nm and that the positive biaxial retardation film (11; 13) has a normal wavelength dispersion or flat wavelength dispersion characteristic, and that the first polarizer plate and the second polarizer plate have internal protective films respectively.