The Pediatric Standing Committee of the Japan College of Rheumatology, in collaboration with the Pediatric Rheumatology Association of Japan, produced guidance on the diagnosis and treatment for juvenile idiopathic arthritis (JIA) for primary care pediatricians and nonpediatric rheumatologists in Japan. This guidance aims to achieve early diagnosis and treatment for JIA, which is similar to adult rheumatoid arthritis (RA), based on recent progress in rheumatology, and to resolve arthritis at an early stage and improve the prognosis of the affected inflammatory joints. It describes clinical symptoms and laboratory findings characteristic to JIA in order to make early diagnosis and treatment possible, and also serves as a triage of patients who are refractory to the treatment protocol described here and need more aggressive interventions. However, because JIA is a complicated and heterogeneous disease and the optimal treatment approach can be diverse and different patient by patient, these guidelines should be viewed as recommendations and be individualized according to the condition of the patient. Finally, we hope that this guidance will trigger exploration for further information by referring to the textbooks and literature listed at the end of these guidelines.