Provided is a prism sheet including a substrate transmitting incident light and having at least one groove inwardly formed in a surface of the substrate. A refractive member is provided in the groove and has a relatively higher refractive index than a refractive index of the substrate. A prism is arranged to face the refractive member, refract and transmit incident light, and has a relatively lower refractive index than the refractive index of the refractive member. A backlight unit is provided that includes at least one light source emitting light, along with a light guide panel that guides a procession of light emitted from the light source. The prism sheet includes at least one groove inwardly formed in a surface of the light guide panel. A refractive member is provided in the groove and a prism is arranged to face the refractive member.