Brain activity can be described by its oscillatory characteristics. It is well known that synchrony in beta-band oscillations (14-28 Hz) in the primary motor cortex decreases during the preparation and execution of a movement. Furthermore, it has been shown that in conditions in which discrete cues display the possible location of upcoming movement targets, the level of desynchronization decreases as the number of cues increases. However, it unclear whether and how beta-band activity is affected by uncertainty about the range of possible directions of movement. We investigated this problem by recording magnetoencephalography while participants performed a cue task. The participant controlled a cursor using a joystick. A spatial cue (0, 90, or 180 deg) indicated the range of possible locations of the upcoming target. The results show that the latency of response increased with cue size. In addition, the synchronization of the beta-band decreased after the presentation of the cue. Most importantly, beta-band desynchronization was greatest for the smallest cue and lowest for the largest cue. These results indicate that beta-band is modulated by the range of directional uncertainty during motor planning.