A method of analyzing an iron concentration of a boron-doped p-type silicon wafer by a surface photo voltage method, which comprises: subjecting the boron-doped p-type silicon wafer to Fe-B pair separation processing by irradiation with light, and determining the iron concentration based on a change in a minority carrier diffusion length following the Fe-B pair separation processing, wherein the iron concentration is calculated with a calculation equation, the calculation equation comprising parameters in the form of a minority carrier diffusion length L AF1 measured by said surface photovoltage method after the separation processing, a minority carrier diffusion length L AF2 measured by said surface photovoltage method after a prescribed time has elapsed following measurement of L AF1, and dependence on time of recombination of Fe-B pairs that have been separated by the separation processing, and the calculation equation is derived by assuming that the irradiation with light causes boron atoms and oxygen atoms that are present in the silicon wafer to form a bonded product, and by assuming that the bonded product has identical influences on L AF1 and L AF2, characterised in that: the calculation equation is the following equation: N Fe = D n F AF 2 − F AF 1 1 C FeB − C Fei 1 L AF 1 2 − 1 L AF 2 2 wherein, in equation, N Fe denotes the iron concentration, F AF1 denotes the dependence on time of recombination of Fe-B pairs calculated from the following equation at the time of measurement of L AF1, F AF2 denotes the dependence on time of recombination of Fe-B pairs calculated from the following equation at the time of measurement of L AF2, C FeB denotes an electron capture coefficient of Fe-B pairs, C Fei denotes an electron capture coefficient of interstitial Fe (Fei), and D n denotes an electron diffusion constant; F = exp − τ C − 1 t wherein, in equation, F denotes dependence on time of recombination of Fe-B pairs, τc denotes a capture ratio, and t denotes a passage of time following irradiation with light. subjecting the boron-doped p-type silicon wafer to Fe-B pair separation processing by irradiation with light, and determining the iron concentration based on a change in a minority carrier diffusion length following the Fe-B pair separation processing, wherein the iron concentration is calculated with a calculation equation, the calculation equation comprising parameters in the form of a minority carrier diffusion length L AF1 measured by said surface photovoltage method after the separation processing, a minority carrier diffusion length L AF2 measured by said surface photovoltage method after a prescribed time has elapsed following measurement of L AF1, and dependence on time of recombination of Fe-B pairs that have been separated by the separation processing, and the calculation equation is derived by assuming that the irradiation with light causes boron atoms and oxygen atoms that are present in the silicon wafer to form a bonded product, and by assuming that the bonded product has identical influences on L AF1 and L AF2, characterised in that: the calculation equation is the following equation: N Fe = D n F AF 2 − F AF 1 1 C FeB − C Fei 1 L AF 1 2 − 1 L AF 2 2 wherein, in equation, N Fe denotes the iron concentration, F AF1 denotes the dependence on time of recombination of Fe-B pairs calculated from the following equation at the time of measurement of L AF1, F AF2 denotes the dependence on time of recombination of Fe-B pairs calculated from the following equation at the time of measurement of L AF2, C FeB denotes an electron capture coefficient of Fe-B pairs, C Fei denotes an electron capture coefficient of interstitial Fe (Fei), and D n denotes an electron diffusion constant; F = exp − τ C − 1 t wherein, in equation, F denotes dependence on time of recombination of Fe-B pairs, τc denotes a capture ratio, and t denotes a passage of time following irradiation with light. the calculation equation is the following equation: N Fe = D n F AF 2 − F AF 1 1 C FeB − C Fei 1 L AF 1 2 − 1 L AF 2 2 wherein, in equation, N Fe denotes the iron concentration, F AF1 denotes the dependence on time of recombination of Fe-B pairs calculated from the following equation at the time of measurement of L AF1, F AF2 denotes the dependence on time of recombination of Fe-B pairs calculated from the following equation at the time of measurement of L AF2, C FeB denotes an electron capture coefficient of Fe-B pairs, C Fei denotes an electron capture coefficient of interstitial Fe (Fei), and D n denotes an electron diffusion constant; F = exp − τ C − 1 t wherein, in equation, F denotes dependence on time of recombination of Fe-B pairs, τc denotes a capture ratio, and t denotes a passage of time following irradiation with light.