Provided is a projection system that sets an arbitrary three-dimensional shape as a projection target and properly corrects geometric distortion of a projected image even when a user's viewpoint is not fixed. A projection unit of the projector apparatus projects a test image for first adjustment. A three-dimensional shape measurement unit measures the three-dimensional shape of the projection target. An image capturing apparatus captures the test image for first adjustment projected by the projection unit to obtain a captured image for first adjustment. A projected image adjustment unit (1) performs first adjustment processing for correcting an image such that geometric image distortion viewed from an imaging point, at which the captured image for first adjustment has been captured, is reduced, based on a captured image for first adjustment obtained by the image capturing apparatus, and (2) performs second adjustment processing for correcting the image such that the geometric image distortion is reduced based on a state in which the image adjusted by the first adjustment processing is projected by the projection unit.