Provided is a novel C-phenyl glycitol compound that may serve as a prophylactic or therapeutic agent for diabetes by inhibiting both SGLT1 activity and SGLT2 activity, thereby exhibiting a glucose absorption suppression action and a urine glucose excretion action. A C-phenyl glycitol compound represented by Formula (I) below or a pharmaceutically acceptable salt thereof or a hydrate thereof wherein R1 and R2 are the same or different and represent a hydrogen atom, a hydroxyl group, a C1-6 alkyl group, a C1-6 alkoxy group or a halogen atom, R3 is a hydrogen atom, a C1-6 alkyl group, a C1-6 alkoxy group or a halogen atom, Y is a C1-6 alkylene group, —O—(CH2)n- (n is an integer of 1 to 4) or a C2-6 alkenylene group, provided that when Z is —NHC(═NH)NH2 or —NHCON(RB)RC, n is not 1, Z is —CONHRA, —NHC(═NH)NH2 or —NHCON(RB)RC,