It was investigated that the effects of multiple tillage treatments on the Tyrophagus similis Volgin (Acari: Acaridae) populations and on the physical properties of soil. From May to June 2014, spinach was cultivated twice in greenhouses in Hokkaido. T. similis was released at a rate of 500/ m² with 50 kg/10 a of fishmeal pellets, 9 days before seeding. After 2 days, the entire area was tilled once, followed by one to three tillage treatments, 1 week before sowing. The density of T. similis in the soil, the number of T. similis acarid mites captured inside the traps, and the degree of damage caused to spinach were significantly lower in the triple-processed land plots than in the unprocessed (control) land plots. No significant difference in the water content was observed between the processed and control plots. However, the weight of the dried soil per 100 ml was significantly higher in the triple-processed land plots than in the controls. This weight did not change when the soil was pressed (48 g/cm²) without being tilled. Moreover, the density of T. similis and the number of T. similis acarid mites captured inside the traps were also significantly lower in the pressed land plots than in the control plots.