Reflection type diffusion device and projection device

The invention provides a reflective diffusion device which comprises a driving part, a reflecting part and a diffusion part and is used for reflecting and diffusing a laser beam emitted by a light source module. The driving element has a rotating shaft. The reflector includes a central axis and is disposed on the driving element. The central axis is collinear with the rotating shaft. The diffusion piece is arranged on at least one part of the reflection piece, and the driving element is used for driving the reflection piece and the diffusion piece to rotate around the central axis. The laser beam enters the diffusion piece along the incidence direction and is transmitted to the reflection piece, and the laser beam is reflected by the reflection piece and exits the diffusion piece along the exit direction to form a diffused beam. An incident included angle is formed between the incident direction and the central axis, an emergent included angle is formed between the emergent direction and the central axis, the