A time synchronization method performed by each node in an ad hoc network in which a plurality of nodes are connected with each other by radio and time synchronization of each node is performed by transmitting and receiving a beacon including time information in a beacon period is provided. The time synchronization method includes: a generation step of generating a slot number using a random number every one beacon period; a determination step of determining whether to cancel beacon transmission based on the slot number when the node does not receive a beacon from another node by beacon transmission time corresponding to the slot number; and a step of canceling beacon transmission when determining to cancel beacon transmission in the determination step, and transmitting a beacon including time information of the own node at the beacon transmission time when determining not to cancel beacon transmission.