Abstract: This application provides a communication method. The communication method includes: A first device sends indication information, where the indication information is used to indicate whether the first device sends a first synchronization signal block in a synchronization slot of a sidelink, and the synchronization slot is used to transmit a synchronization signal block; and the first device sends first data in the synchronization slot of the sidelink. Because the first device indicates a sending behavior of the first device in the synchronization slot before sending the first data, a receiver may determine a processing manner of the receiver in the synchronization slot based on the indication information.