The lactosucrose high-content powder according to the present invention is prepared by allowing an aqueous solution containing sucrose and lactose to act on a saccharide-transferring enzyme, removing concomitant saccharides in the resultant saccharide solution containing lactosucrose to obtain a lactosucrose high-content solution with a lactosucrose content of 45 w/w % or higher on sugar composition, and spray-drying the resultant solution to obtain a lactosucrose high-content powder. The powder is incorporated in an orally- or parenterally-administrable product to obtain an orally- or parenterally-administrable product which exerts a selective growth-promoting-effect on a microorganism of the genus Bifidobacterium in vivo.