Provided is an encoder which includes circuitry and memory. Using the memory, the circuitry: splits an image block into a plurality of partitions; generates a motion vector candidate list; obtains a motion vector from the motion vector candidate list; performs inter prediction processing using the motion vector; and encodes the image block using a result of the inter prediction processing. When a partition is a non-rectangular partition, the circuitry generates the motion vector candidate list using at least one motion vector among a plurality of motion vectors for a plurality of spatially neighboring partitions or a plurality of motion vectors for a plurality of temporally neighboring partitions, without using a plurality of motion vectors for a plurality of sub-partitions.