The present invention provides a 1,4-disubstituted imidazole derivative of formula (1') wherein ring Q1 is optionally-substituted C6-10 aryl group, etc.； R1 and R2 are independently hydrogen atom, etc.； W1 is optionally-substituted C1-4 alkylene group； W2 is -NR3aC(O)- wherein R3a is hydrogen atom or C1-6 alkyl group, etc.； ring Q2 is 5- to 10-membered heteroaryl group, etc.； W3 is optionally-substituted C1-4 alkylene group, etc.； n is 1, 2, 3, 4, or 5； R4 is independently halogen atom, optionally-substituted C1-6 alkyl group, etc.； R5 is hydroxy group, etc.； and a pharmacologically acceptable salt thereof, which have a potent inhibitory effect on the sphere-forming capacity of cancer cells and are useful as an orally-available anti-tumor agent.
