This paper deals with the Microstrip Circular Patch Antenna for WLAN / WiMAX Application. The proposed antenna operates at WiMAX / WLAN frequency bands. The proposed antenna has the substrate of Glass Epoxy FR4 with dielectric constant of 4.3 and patch diameter of 34mm with dielectric loss of 0. The Coaxial feeding technique is used to feed the antenna with 75 ohm impedance. The radiation performance, such as VSWR, Return loss, Radiation pattern and Gain of the antenna are simulated using ANTENNA MAGUS 5.2.