The invention provides a photoelectric detection device and a method thereof as well as photoresist coating equipment, relates to the technical field of production of displayers and aims to solve the problems that time consumptionand labor consumptionare high and judgment inaccuracy is easy to cause during detecting shell mura. The photoelectric detection device comprises a light source and a receiving processor, wherein the light source is used for generating detectionlight beams and projecting the detectionlight beams to a transparent substrate; the receiving processor is fixed opposite to the light source, located behind the light source and used for receiving first reflection light generated by a reflection detection light beam on the upper surface of the transparent substrate and second reflection light generated by a reflection detection light beam on the lower surface of the transparent substrate and obtaining measurement light path difference; the measurement light path difference is difference between a light path of the first reflection light and a light path of the second reflection light; the receiving processor is also used for judging whether the light path difference meets a preset condition and determining that water ripples are formed in the transparent substrate when the measurement light path difference cannot meet the preset condition. The photoelectric detection device is applied to detection of shell mura.