An object of the present invention is to provide a highly safe catheter for measuring electric potential that can be inserted into a cardiac chamber together with a balloon-tip ablation catheter and is able to prevent abnormal heat generation at electric potential-measuring electrodes even when high-frequency current is distributed. The present invention provides an catheter for measuring electric potential, comprising: a shaft having electric potential-measuring electrodes, a metal portion with a length of 2 mm or more, and a lumen passing therethrough from a proximal end to a distal end in the longitudinal direction and a metal wire inserted through the lumen and connected to the metal portion.
