An earth leakage detection unit, comprising: a zero-phase current transformer that has an annular core; load side conductors (11T to 11N) that are arranged on either one side in an axial direction of the zero-phase current transformer, corresponding to respective phases of load side terminals; power supply side conductors (12T to 12N) that are arranged on the other side in the axial direction of the zero-phase current transformer, corresponding to respective phases of a power supply side circuit; through conductor portions among which a through conductor portion (s) corresponding to one phase or two phase is/are continuously fixed to either one(s) of a load side conductor(s) among the load side conductors and a power supply side conductor(s) among the power supply side conductors, and among which through conductor portions corresponding to the other phases are continuously fixed to the other ones of the other load side conductors and the other power supply side conductors, and each of which penetrates the annular core of the zero-phase current transformer to be joined to a joining portion of one of the load side conductors and the power supply side conductors that has a corresponding phase and to which any one of the through conductor portions is not continuously fixed; and insulating coating portions (17T to 17N, 18T to 18N) each of which is formed at least on the outside of a portion of the through conductor portion continuously fixed to one of the load side conductors and the power supply side conductors at which one of the through conductor portions is continuously fixed, wherein the number of the phases of the load side terminals is four and the number of the phases of the power supply side circuit is four, and characterised in that two of the through conductor portions are continuously fixed to two of the power supply side conductors disposed at diagonal positions with respect to an inner hole of the annular core, respectively, and other two of the through conductor portions are continuously fixed to two of the load side conductors disposed at diagonal positions with respect to the inner hole of the annular core, respectively. a zero-phase current transformer that has an annular core; load side conductors (11T to 11N) that are arranged on either one side in an axial direction of the zero-phase current transformer, corresponding to respective phases of load side terminals; power supply side conductors (12T to 12N) that are arranged on the other side in the axial direction of the zero-phase current transformer, corresponding to respective phases of a power supply side circuit; through conductor portions among which a through conductor portion (s) corresponding to one phase or two phase is/are continuously fixed to either one(s) of a load side conductor(s) among the load side conductors and a power supply side conductor(s) among the power supply side conductors, and among which through conductor portions corresponding to the other phases are continuously fixed to the other ones of the other load side conductors and the other power supply side conductors, and each of which penetrates the annular core of the zero-phase current transformer to be joined to a joining portion of one of the load side conductors and the power supply side conductors that has a corresponding phase and to which any one of the through conductor portions is not continuously fixed; and insulating coating portions (17T to 17N, 18T to 18N) each of which is formed at least on the outside of a portion of the through conductor portion continuously fixed to one of the load side conductors and the power supply side conductors at which one of the through conductor portions is continuously fixed, wherein the number of the phases of the load side terminals is four and the number of the phases of the power supply side circuit is four, and characterised in that two of the through conductor portions are continuously fixed to two of the power supply side conductors disposed at diagonal positions with respect to an inner hole of the annular core, respectively, and other two of the through conductor portions are continuously fixed to two of the load side conductors disposed at diagonal positions with respect to the inner hole of the annular core, respectively.