Flexible decision making is an indispensable ability for humans. Although neurons in decision-related cortex accumulate relevant information preferentially depending on context, how sensory information represented in sensory cortex is conveyed to decision-related cortex remains unclear. To elucidate this question, we investigated the functional connectivity between sensory cortex (area MT) and decision-related cortex (area LIP) by recording simultaneously from both areas using two electrodes while monkeys performed a switching task.Two Japanese macaques were trained to flexibly switch between a direction discrimination task and a depth discrimination task. We recorded local field potential in areas MT and LIP simultaneously. A random dot stimulus optimized to the preference of MT neurons was presented in the receptive field of that neuron. One of two choice targets was placed within the response field of the LIP neuron.To examine whether synchronous oscillation changed depending on MT-LIP pairs connection, we grouped the pairs by task relevance into two groups, “Task congruent pairs” and “Task incongruent pairs”. We found that gamma-band bottom-up synchrony was significantly larger in task congruent pairs than in task incongruent pairs during decision formation. Furthermore, in incongruent MT neurons where task relevant connections changed depending on the instructed task, gamma-band synchrony enhanced only in task-relevant MT-LIP connections.These results suggest that the gamma-band synchrony from area MT to LIP is related to context-dependent decision making. This oscillation might enhance task-relevant connections according to task requirement for flexible decision making.