A method for evaluating concentration of defect in silicon single crystal substrate, defect being formed by particle beam irradiation in silicon single crystal substrate, including the steps of: measuring a resistivity of silicon single crystal substrate, followed by irradiating silicon single crystal substrate with particle beam, re-measuring resistivity of silicon single crystal substrate after irradiation; determining each carrier concentration in silicon single crystal substrate before and after irradiation on basis of measured results of resistivity before and after particle beam irradiation to calculate rate of change of carrier concentration; and evaluating concentration of VV defect on basis of rate of change of carrier concentration, VV defect being made of a silicon atom vacancy and being formed by particle beam irradiation in silicon single crystal substrate. The method can simply evaluate concentration of VV defect formed in silicon single crystal substrate by particle beam irradiation.