Dielectric constant estimation device and microwave heating apparatus provided with dielectric constant estimation device

A dielectric constant estimation device which can estimate a dielectric constant of an object with high accuracy in a non-contact state even when a shape of the object is indefinite, and a microwave heating device equipped with the dielectric constant estimation device. The dielectric constant estimation device includes a transmitting antenna and a receiving antenna which can switch a polarized wave of an electromagnetic wave between a TE wave and a TM wave. Based on a reflected wave of the TE wave and a reflected wave of the TM wave from the object, the dielectric constant estimation device calculates a TM/TE reflection ratio, and compares the calculated TM/TE reflection ratio and dielectric constant data of theoretical values stored in a memory part in advance in the form of database with each other so that a dielectric constant of the object is estimated.