[Problems] It is intended to provide a storing device which is convenient in preserving a slice of a pathological tissue or the like over a long time and by which a required number of slices can be quickly provided without waste. It is also intended to provide an instrument for microscopic observation which is equipped with this storing device and a transparent plate having an adhesive layer formed thereon. [Means for Solving Problems] A device comprising: a piece of a resin film on which a slice having been excised from a sample block or a cell block slice is adhered and fixed via an adhesive layer provided on the surface thereof; and a holder on the surface of which the back face of the film piece is detachably adhered and fixed via a pressure-sensitive adhesive layer. An instrument for microscopic observation which comprises the storing device and a transparent plate for adhering and fixing the film piece having been peeled off from the storing device.