Provided are a diamond polycrystalline body having a longer life than conventional diamond polycrystalline bodies when it is slid, a method for manufacturing the same, and a tool. In a diamond polycrystalline body (2), at least one element whose oxide has a melting point of less than or equal to 1000°C is added thereto, and crystal grains have an average grain size of less than or equal to 500 nm. Thereby, wear of diamond can be suppressed, and the diamond polycrystalline body can have a longer life when it is slid.