A modified bio-related substance, wherein at least one poly(alkylene glycol)oxy group represented by the following formula (1) is combined in a molecule: wherein R is a hydrocarbon group having 1 to 24 carbon atoms, OA1 and OA2 are each an oxyalkylene group having 2 to 4 carbon atoms, the groups represented by R are the same or different from each other in one molecule, and the groups represented by OA2 are the same or different from each other in one molecule, n and m are each average number of moles of the oxyalkylene group added, n represents 0 to 1000, and m represents 10 to 1000.