A method for estimating a posture of a camera installed in a substrate processing apparatus to obliquely photograph an object includes removing the remaining background other than a substrate and performing ellipse fitting, adjusting a yaw direction of the camera by using a difference between the center of a camera image and the center of an elliptical substrate image obtained by performing the ellipse fitting, adjusting a roll direction of the camera by using a tilt angle of an ellipse in the elliptical substrate image obtained by performing the ellipse fitting, and adjusting a pitch direction of the camera by using a ratio of a minor axis to a major axis of the ellipse in the elliptical substrate image obtained by performing the ellipse fitting.