Common mode filter

A common mode filter comprising:

• a magnetic substrate;
• a coil pattern formed on the magnetic substrate;
• a dielectric layer formed on the magnetic substrate so as to cover an upper part, a lower part and a side surface of the coil pattern;
• and
• a first coupling agent having at least two functional groups so as to be bonded to the magnetic substrate and the dielectric layer, respectively, through the at least two functional groups that are different from one another and interposed between the magnetic substrate and the dielectric layer so as to prevent the magnetic substrate and the dielectric layer from being separated.