Novel compounds below are useful for preventing or treating diseases caused by protozoans. At least one of a compound represented by Formula (I) (wherein, X represents a hydrogen atom or a halogen atom R 1 represents a hydrogen atom R 2 represents a hydrogen atom or a C 1-7 alkyl group R 3 represents -CHO, -C(=O)R 5 , -COOR 5 (wherein R 5 represents a C 1-7 alkyl group), -CH 2 OH or -COOH and R 4 represents a C 1-16 alkyl group having one or more substituents on a terminal carbon atom and/or non-terminal carbon atom(s), a C 2-16 alkenyl group having one or more substituents on a terminal carbon atom and/or non-terminal carbon atom(s), or a C 2-16 alkynyl group having one or more substituents on a terminal carbon atom and/or non-terminal carbon atom(s)), an optical isomer thereof, and a pharmaceutically acceptable salt is used.
