A developing treatment method includes: a treatment solution supplying step of supplying a treatment solution made by diluting a hydrophobizing agent hydrophobizing a resist pattern with hydrofluoroether onto a substrate on which a rinse solution has been supplied after development of the resist pattern; a hydrophobic treatment stabilizing step of stabilizing a hydrophobic treatment of the resist pattern with the supply of the treatment solution stopped and rotation of the substrate almost stopped; and a treatment solution removing step of removing the treatment solution from a top of the substrate on which the treatment solution has been supplied. The hydrophobizing agent is trimethylsilyldimethyl-amine.