The aim of this study was to investigate the reliability and the validity of the Japanese version of the 2010 American College of Rheumatology Preliminary Diagnostic Criteria for Fibromyalgia (ACR 2010-J), and its quantification scale, the Fibromyalgia Symptom Scale (FS-J). In this study, we divided patients with chronic pain without psychiatric disorders other than depression into two groups according to the 1990 ACR Diagnostic Criteria for Fibromyalgia, a fibromyalgia group and a non-fibromyalgia group (rheumatoid arthritis, osteoarthritis, and gout). Patients in both groups were assessed using the ACR 2010-J and FS-J. Seventy-seven of 94 (82%) patients in the fibromyalgia group met the ACR 2010-J, whereas 9% (4/43) of the non-fibromyalgia group did so, with a sensitivity of 82%, specificity of 91%, positive predictive value of 95%, negative predictive value of 70%, and positive likelihood ratio of 8.8. Mean total scores on the FS-J significantly differentiated the fibromyalgia from the non-fibromyalgia group. The scale had high inter-rater reliability and high internal consistency. With a cutoff score of 10, the positive likelihood ratio was 10.1. Our findings indicate that the ACR 2010-J and FS-J have high reliability and validity, and are useful for assessing fibromyalgia in Japanese populations with chronic pain. As regards the positive likelihood ratio, that of the FS-J might be suitable as a positive test.