To improve positioning accuracy of an alignment device.

The alignment device positioning a pair of substrates superposed on each other includes: a substrate holding part holding one side of the pair of substrates; a moving stage supporting the other side of the pair of substrates and moving in a direction parallel to a surface of the one-side substrate; a microscope arranged on the moving stage and imaging the image of the one-side substrate; a position calculation part calculating the position of the one-side substrate based on the image imaged by the microscope; an inclination detection part detecting the value of the inclination of the microscope when the microscope images the image; a measurement error calculation part calculating a measurement error of the position of the microscope based on the value of the inclination of the microscope detected by the inclination detection part; and a position correction part calculating a corrected position obtained by correcting the position calculated by the position calculation part based on the measurement error calculated by the measurement error calculation part.