A device of measuring a physical state of a material by spectrum is provided. The device includes a first action path, a detector, a processing unit, a control unit, a memory unit, and an artificial intelligence unit. The detector is configured to detect a spectrum of an other material in a plasma state during a deposition process of a material to be measured in the first action path. The processing unit is configured to obtain a deposition state of the material to be measured during the deposition process based on the spectrum of the other material in the plasma state, a chemical reaction between the other material and the material to be measured, and a relation of supplied mole quantity between the other material and the material to be measured. A method of measuring a physical state of a material by spectrum is also provided.