An electric current measuring device configured to cause a plurality of current transformers (CT1,...,CT4) provided to a respective plurality of power lines (PL1,...,PL4) to measure electric currents flowing through the plurality of power lines (PL1,...,PL4), said electric current measuring device comprising: at least one electricity storing section configured to store electricity by use of electric currents from the plurality of current transformers (CT1,...,CT4) provided to the respective plurality of power lines (PL1,...,PL4); an electric current measuring section configured to measure, in accordance with the electric currents from the plurality of current transformers (CT1,...,CT4), the electric currents flowing through the plurality of power lines (PL1,...,PL4) provided with the respective plurality of current transformers (CT1,...,CT4); and a control section configured to carry out control so that the electric current measuring section carries out the measurement in accordance with an electric current from one of the plurality of current transformers (CT1,...,CT4) and repeats the measurement for each of the plurality of current transformers (CT1,...,CT4), the electric current measuring section and the control section each operating by use of electric power from the at least one electricity storing section, characterized in that the electric current measuring device further comprises a plurality of switching sections (20a,...,20d) configured to switch between the at least one electricity storing section and the electric current measuring section to either of which the electric currents from the plurality of current transformers (CT1,...,CT4) are to flow, wherein the control section carries out control so that any one of the plurality of switching sections (20a,...,20d) is selected, the selected one of the plurality of switching sections (20a,...,20d) causes an electric current from a corresponding current transformer (CT1,...,CT4) of the plurality of current transformers (CT1,...,CT4) to flow to the electric current measuring section, whereas the other unselected switching sections (20a,...,20d) cause electric currents from respective current transformers (CT1,...,CT4) of the plurality of current transformers (CT1,...,CT4) to flow to the at least one electricity storing section, and the selection is carried out successively with respect to each of the plurality of switching sections (20a,...,20d). at least one electricity storing section configured to store electricity by use of electric currents from the plurality of current transformers (CT1,...,CT4) provided to the respective plurality of power lines (PL1,...,PL4); an electric current measuring section configured to measure, in accordance with the electric currents from the plurality of current transformers (CT1,...,CT4), the electric currents flowing through the plurality of power lines (PL1,...,PL4) provided with the respective plurality of current transformers (CT1,...,CT4); and a control section configured to carry out control so that the electric current measuring section carries out the measurement in accordance with an electric current from one of the plurality of current transformers (CT1,...,CT4) and repeats the measurement for each of the plurality of current transformers (CT1,...,CT4), the electric current measuring section and the control section each operating by use of electric power from the at least one electricity storing section, characterized in that the electric current measuring device further comprises a plurality of switching sections (20a,...,20d) configured to switch between the at least one electricity storing section and the electric current measuring section to either of which the electric currents from the plurality of current transformers (CT1,...,CT4) are to flow, wherein the control section carries out control so that any one of the plurality of switching sections (20a,...,20d) is selected, the selected one of the plurality of switching sections (20a,...,20d) causes an electric current from a corresponding current transformer (CT1,...,CT4) of the plurality of current transformers (CT1,...,CT4) to flow to the electric current measuring section, whereas the other unselected switching sections (20a,...,20d) cause electric currents from respective current transformers (CT1,...,CT4) of the plurality of current transformers (CT1,...,CT4) to flow to the at least one electricity storing section, and the selection is carried out successively with respect to each of the plurality of switching sections (20a,...,20d).