Proposed is a method for a first device to perform wireless communication. The method may include a step for generating a sidelink synchronization signal block (S-SSB) including a sidelink primary synchronization signal (SPSS), a sidelink secondary synchronization signal (SSSS), and a sidelink physical broadcast channel (PSBCH), and transmitting the S-SSB to a second device. For example, at least one of an SPSS-related symbol period, an SSSS-related symbol period, or a PSBCH-related symbol period may include a transition period. For example, the transition period may be determined on the basis of at least one of the priority of the SPSS, the priority of the SSSS, or the priority of the PSBCH.