Pohang Accelerator Laboratory(PAL) had developed an U10 undulator to utilize low energy synchrotron radiation at Pohang Light Source (PLS). The U10 is a hybrid type device with 10cm period, minimum gap of 16mm, maximum flux density of 1.49 Tesla, 1625mm total magnetic structure length. The support locations and structure of an insertion device are optimized to achieve a minimum deflection due to the magnetic loads. First, Finite Element Analysis (FEA) are performed on the backing beam, support and drive structures of the insertion device under expected magnetic load of 10 tons to determine the maximum deflection and optimal support locations. To reduce the deflection further, springs that compensate the gap dependent magnetic loads are designed and implemented. The optimized maximum deflections are estimated to be about 20µm while the deflections before optimization are 214µm.