PROBLEM TO BE SOLVED: To provide a plant growth promotion agent comprising a plant growth promotion rhizosphere-bacteria and to provide a plant cultivation method using the same.SOLUTION: A plant growth promotion agent comprising microorganisms belonging to Polaromonas, Variovorax, Novosphingobium, Nocardioides, Devosia, Mesorhizobium, the Sphingomonas, Phyllobacterium, Bacillus, Rhizobium, or Streptomyces is inoculated into seeds or seedlings of crops.