Problem to be solved. To provide early measures against cognitive disorder, more specifically, novel food materials capable of maintaining or improving present state of cognitive function prior to the decline of cognitive function. Solution. Disclosed is an agent for improving cognitive function comprising cells of Bifidobacterium sp. Strain N61 (NITE BP-02214) as an effective part. Also provided is an agent for improving cognitive function in a unit serving form containing strain N61 as an effective ingredient in the unit.