The compost sieve is a mobile device for efficient composting. The machine has a receiving chamber and the dosage of the material in the drum is performed by a dispenser within the chamber. After the chambers, the waste goes into the sieving drum. On the sieve drum, there is a perforation of technological rectangular openings through which the small fraction of the compost is sieved. Within the drum is a spiral that transports the compost to the output end of the device. For additional dispersion of compost, and therefore better sieving, on the circumference of the drum, steel coils are placed in between the spiral. The small fraction falls on the longitudinal conveyor located beneath the sieve, while the raw fractions that have not gone through the perforation of the sieve fall on the transversal transporter. The drum is easily interchangeable and manipulated which allows sifting of different sizes.