In recent years, the problem of antimicrobial resistance (AMR) from inappropriate use of antimicrobial drugs has emerged, and a plan to counter AMR has been formulated. From October 2017, our hospital started interventions to guide prescribing physicians in the proper use of intravenous antibiotics for patients requiring said treatment for more than 15 days. In the present study, we investigated the status of treatment with intravenous antibiotics and considered the effects of intervention. This study targeted a total of 2627 patients, 1971 of whom were hospitalized, who started using intravenous antibiotics from June 2017 to January 2018. We assigned those who started between June and September 2017 to the pre-intervention group and those who started between October 2017 and January 2018 to the post-intervention group. The number of patients using long-term intravenous antibiotics, total number of days of treatment, antimicrobial use density (AUD), day of therapy (DOT), and rate of use by lineage of antibiotics were compared. The number of patients using long-term intravenous antibiotics decreased to 40 in the pre-intervention group and 31 in the post-intervention group. There was no significant difference in the total number of treatment days, which was 5.1 ± 5.5 days before and 4.8 ± 4 9 days after, in the intervention group. The AUD of penicillin antibiotics increased and that of aminoglycosides decreased. Furthermore, the DOT of third-generation cephems and lincomycin decreased. Penicillin had an increased lineage use ratio, while that for thirdgeneration cephems, carbapenems, and lincomycin decreased. The number of patients using long-term intravenous antibiotics as well third-generation cephem and carbapenem antibiotics, which are broad spectrum antibiotics, decreased; the overall use of penicillin, a narrow-spectrum antimicrobial, increased. This suggested that the intervention resulted in the promotion of proper use of antimicrobial drugs.