The objective of the present study was to assess management procedures and biosecurity practice on swine commercial farms during the period that porcine epidemic diarrhea occurred in Japan. A questionnaire survey was conducted to ask the production system, management procedures, and biosecurity practice to farms that consulted clinical veterinarians affiliated with the Japan Association of Swine Practitioners. As a result, we obtained answers from 258 farms. The 258 farms were categorized into three groups based on the average swine inventory:small (≤2000 pigs;n＝86), middle (2001 to 4000 pigs;n＝82) and large (≥4001 pigs;n＝90). Large group had a higher proportion of farms with windowless house in gestation barn, farrowing barn, weaning barn, and finishing barn than small group (P<0.05). Large group had a higher proportion of farms performing all-in/all-out than small group (farrowing barn:58.0 vs. 11.1%, weaning barn:80.7 vs. 29.1%, and finishing barn:60.5 vs. 12.8%;P<0.05). Large group had a higher proportion of farms performing shower-in and shower-out than small group (shower-in:55.4 vs. 5.8%, shower-out:70.0 vs. 22.1%;P<0.05). The proportion of farms washing truck before loading was 63.8%, and large group had a higher proportion of farms than small group (P<0.05). In conclusion, it was revealed that the farm biosecurity for epidemic prevention was strengthened at the large-scale farm as compared with the small farm.