Abstract: Provided is a magnetic core having an appropriate range of permeability and a high magnetic flux density, thereby being configured to have a small phase difference and a small size. The magnetic core can be use for electric current sensors. The magnetic core is made of an amorphous alloy having a composition represented by the general formula: FeaMbSicBdM?e, in which M is at least one element that is selected from Ni and Co, and M? is Cr, and a to e are atomic % and numbers satisfying 30?a?80, 1?b?50, 0.1?c?20, 0.1?d?20, and 0?e?10, respectively, and wherein the amorphous alloy has a magnetic flux density of 1.2 T to 1.7 T, and a permeability of 1,000 to 4,000.