Position setting method of thickness measurer, and grinding apparatus

A grinding apparatus configured to grind a substrate, comprising:

• a substrate holder;
• a grinder, having a grinding whetstone configured to grind the substrate holder or the substrate held by the substrate holder, configured to move the grinding whetstone relative to the substrate or the substrate holder;
• a thickness measurer configured to measure a thickness of the substrate by using measurement light;
• and
• a controller,
• wherein the controller controls:
• holding a calibration substrate with the substrate holder;
• irradiating the calibration substrate with the measurement light from the thickness measurer, while moving the thickness measurer closer to or away from the calibration substrate;
• acquiring, from the thickness measurer, intensity of reflection light of the measurement light reflected on the calibration substrate;
• and
• setting a position of the thickness measurer at which the acquired intensity of the reflection light becomes an optimal value as a thickness measurement position of the substrate.