The present invention provides a compound which has the effect of PDE 10A inhibition, and which is useful as a medicament for preventing or treating schizophrenia or so on. A compound represented by the formula (1&prime；): wherein, Ring A&prime； represents an optionally substituted pyridine ring, an optionally substituted pyridazine ring, a pyrimidine ring, or 10 a pyrazine ring, R1&prime； represents (1) wherein, R1a&prime； represents an optionally substituted phenyl group, or an optionally substituted 5- to 10-membered heterocyclic group, Ring B2 represents a bond, &mdash；S&mdash；, -0-, &mdash；CO&mdash；, an optionally substituted methylene group, or &mdash；NRa&prime；&mdash； (Ra&prime； represents a hydrogen atom, or an optionally substituted C1-6 alkyl group), and Ring B1&prime； represents an optionally further substituted 6- to 10-membered aromatic hydrocarbon ring, or an optionally further substituted 5- to 10-membered aromatic heterocyclic ring, or alternatively, L&prime； and R1a&prime； may be taken together to form an optionally substituted bicyclic or tricyclic fused heterocyclic group, or (2), wherein, R1b&prime； represents an optionally substituted phenyl group, or an optionally substituted 5- to 10-membered heterocyclic group, Ring B2&prime； represents an optionally substituted benzene ring, an optionally substituted pyridine ring, an optionally substituted pyrimidine ring, an optionally substituted pyrazine ring, or an optionally substituted pyridazine ring, Ring D&prime； represents an optionally further substituted 5- or 6-membered ring, R2&prime； represents a hydrogen atom, or a substituent, X&prime； represents &boxH；N&mdash； or &boxH；CRb&prime；&mdash；(Rb&prime； represents a hydrogen atom, or a substituent), - - - - - represents that Rb&prime； and R2&prime； may form, taken together with the carbon atom and the nitrogen atom to which they are each adjacent, an optionally substituted 5- to 7-membered ring when.X&prime； is &boxH；CRb&prime；, or a salt thereof
