Provided are condensed 5-oxazolidinone derivatives and pharmaceutically permissible salts thereof, which have excellent anticoagulant effects, are well absorbed orally, and are useful as therapeutic drugs for thrombosis, etc. Compounds represented by formula (1) and pharmaceutically permissible salts thereof. [In the formula, L represents a C 1 -C 4 alkylene group that may be substituted R 11 and R 12 each independently represent a hydrogen atom or C 1 -C 6 alkyl group, etc. that may be substituted X 1 represents N or CR 1 R 1 and R 2 each independently represent a hydrogen atom, halogen atom, or C 1 -C 6 alkyl group R a represents a C 4 -C 7 cycloalkyl group, etc. that may be substituted and R b represents a hydrogen atom, etc.]
