A novel approach is proposed for reflectarray antenna design which makes use of planar near field measurements to characterize the scatterers and the incident field on the structure. This method is based on an equivalent transmission line model of a unit cell in an infinite periodic array. A monopole probe is used to sense a scattered signal in the near field of a reflectarray illuminated by a primary source. These measurements are introduced in the model and provide all the necessary data to accomplish the design. The method has been validated experimentally with four prototypes based on different levels of approximation, at a central frequency of 15 GHz. The results indicate that the proposed near-field based technique allows the design of reflectarrays having similar or better performance than those obtained when numerical modeling is used to obtain the phase response of the unit cells.