An out-of-head localization filter determination system comprising: an output unit configured to be worn on a user and output sounds to an ear of the user; a microphone unit configured to be worn on the ear of the user and pick up the sounds output from the output unit; a measurement unit configured to output a measurement signal to the output unit and measure a sound pickup signal output from the microphone unit; a data storage unit configured to store first preset data related to spatial acoustic transfer characteristics from a sound source to an ear of a person being measured and second preset data related to ear canal transfer characteristics of the ear of the person being measured in association with each other, and store a plurality of first and second preset data acquired for a plurality of persons being measured; a frequency characteristics acquisition unit configured to convert the sound pickup signal into a frequency domain and acquire frequency characteristics; an extreme value extraction unit configured to extract local maximum values and local minimum values of the frequency characteristics; an envelope calculation unit configured to calculate first envelope data which is based on the local maximum values by interpolating the local maximum values and second envelope data which is based on the local minimum values by interpolating the local minimum values; a comparison unit configured to compare a user feature quantity which is based on the first and second envelope data with each of a plurality of feature quantities which are based on the plurality of pieces of second preset data; an extraction unit configured to extract the first preset data based on the comparison result in the comparison unit; and a determination unit configured to determine a filter in accordance with the first preset data that has been extracted. an output unit configured to be worn on a user and output sounds to an ear of the user; a microphone unit configured to be worn on the ear of the user and pick up the sounds output from the output unit; a measurement unit configured to output a measurement signal to the output unit and measure a sound pickup signal output from the microphone unit; a data storage unit configured to store first preset data related to spatial acoustic transfer characteristics from a sound source to an ear of a person being measured and second preset data related to ear canal transfer characteristics of the ear of the person being measured in association with each other, and store a plurality of first and second preset data acquired for a plurality of persons being measured; a frequency characteristics acquisition unit configured to convert the sound pickup signal into a frequency domain and acquire frequency characteristics; an extreme value extraction unit configured to extract local maximum values and local minimum values of the frequency characteristics; an envelope calculation unit configured to calculate first envelope data which is based on the local maximum values by interpolating the local maximum values and second envelope data which is based on the local minimum values by interpolating the local minimum values; a comparison unit configured to compare a user feature quantity which is based on the first and second envelope data with each of a plurality of feature quantities which are based on the plurality of pieces of second preset data; an extraction unit configured to extract the first preset data based on the comparison result in the comparison unit; and a determination unit configured to determine a filter in accordance with the first preset data that has been extracted.