The invention discloses a photolithography exposure device for implementing off-axis illumination by using a free-form surface lens. The photolithography exposure device comprises a laser source, a beam expander, a free-form surface lens beam shaper, a filtering diaphragm, a varifocal optical system, an optical integrator, a collimation optical system, a field diaphragm, a relay optical system, a mask, a photolithography projection objective and photoresist, wherein the relay optical system comprises a front lens group, a middle reflection lens and a rear lens group; the position of the filtering diaphragm and the position of the front surface of the optical integrator form a pair of conjugate positions of the varifocal optical system; the position of the rear surface of the optical integrator and the position of the field diaphragm form a pair of conjugate positions of the collimation optical system; the position of the field diaphragm and the position of the mask form a pair of conjugate positions of the relay optical system; and the position of the mask and the position of the photoresist form a pair of conjugate positions of the photolithography projection objective. The photolithography exposure device has the advantages of good shaping effect and high energy utilization rate.