A three-dimensional data encoding method includes: encoding, for each of second units, information about positions of three-dimensional points included in a first unit, to generate encoded data items, the second units being smaller than the first unit that is an encoding unit; and outputting the encoded data items. Each of the encoded data items includes no individual additional information. The encoded data items include common additional information. The common additional information includes first information indicating a size of a first encoded data item included in the encoded data items.