The invention relates to a compact particle treatment device with magnetic resonance guiding. The compact particle treatment device comprises a first particle cyclotron apparatus and a first particle beam flow control apparatus matching the first particle cyclotron apparatus, and further comprises a first magnetic resonance imaging apparatus, wherein the first magnetic resonance imaging apparatus is provided with a first main magnet capable of generating a uniform main magnetic field, the first particle cyclotron apparatus mainly comprises a first D-type box group which is disposed in the first main magnetic field and is vertical to the direction of the magnetic line of the first main magnetic field, and the first D-type box group is provided with a first particle source for providing particles therefore and a first lead-out electrode capable of introducing a particle beam flow after acceleration into the particle beam flow control area of the first particle beam flow control apparatus. The radiotherapy device provided by the invention carries out particle beam flow guiding by taking magnetic resonance imaging as a basis, and the device is compact in structure, small in size and low in cost and can better track motion of a treatment target area in real time.