A synchronous spacer with a guiding block comprises strip-shaped links, a plurality of spacer elements, and a guiding block fixed at the end of the links. An arch-shaped surface is formed on the guiding block and is located correspondingly to inner surface of the track of the linear guideway, the guiding block is larger than spacer element of the synchronous spacer but is smaller than the rolling elements. With the guidance of the guiding block, the synchronous spacer is prevented from impacting the inner surface of the track, enabling the linear guideway to move smoothly and stably.