A three-dimensional data encodes method of encoding three-dimensional data items in time series. Each of the three-dimensional data items includes a geometry information item and an attribute information item in association with a same time point. The three-dimensional data encoding method includes: first encoding of encoding the geometry information item; and second encoding of encoding the attribute information item with reference to the geometry information item associated with the same time point. The geometry information item and the attribute information item that are in association with the same time point are included in an access unit.