A projection apparatus with locking structure includes an apparatus case including a main casing, a lid and at least one locking structure at the main casing and the lid, a light source, a light valve and a lens. The structure includes a slot having two opposite ends at the casing, at-least one elastic arm in the slot and at-least one positioning pillar at the lid. When the lid covers the main casing and the pillar extends into the first end, by rotating the lid relatively to the main casing, the pillar moves along the slot to the second end; when the pillar is at the second end, the elastic arm limits the pillar at the second end. The light source is for providing an illumination beam. The light valve and lens are for respectively converting the illumination beam into an image beam and the image beam into a projection beam.