An apparatus for measuring a distance between eye tissues comprising: an interfering optical system that includes a light source, a beam splitter for splitting light emitted from the light source into first split light and second split light, an emitting optical system for projecting at least one of the first split light and the second split light toward an examinee's eye, a light receiving optical system for combining the two pieces of split light including the split light reflected by the examinee's eye and guiding the combined light to a light receiving device, and a driving part for moving an optical member in order to adjust an optical path difference between the first split light and the second split light; characterized by a mode switching unit that issues a mode switching signal for switching a measurement mode between at least two measurement modes including a first measurement mode for measuring the ocular axial length of the examinee's eye while moving the optical member at a first scanning rate, and a second measurement mode for measuring the ocular axial length of the examinee's eye while moving the optical member at a second scanning rate which is slower than the first scanning rate; and a calculation and control unit that performs operations of changing a scanning rate of the optical member at the time of measurement in accordance with the mode switching signal issued by the mode switching unit, controlling an operation of the driving part such that the optical member is moved at a scanning rate corresponding to the measurement mode switched by the mode switching unit, and measuring the ocular axial length of the examinee's eye, based on an output signal of the light receiving device, obtained at the time of moving the optical member. an interfering optical system that includes a light source, a beam splitter for splitting light emitted from the light source into first split light and second split light, an emitting optical system for projecting at least one of the first split light and the second split light toward an examinee's eye, a light receiving optical system for combining the two pieces of split light including the split light reflected by the examinee's eye and guiding the combined light to a light receiving device, and a driving part for moving an optical member in order to adjust an optical path difference between the first split light and the second split light; characterized by a light source, a beam splitter for splitting light emitted from the light source into first split light and second split light, an emitting optical system for projecting at least one of the first split light and the second split light toward an examinee's eye, a light receiving optical system for combining the two pieces of split light including the split light reflected by the examinee's eye and guiding the combined light to a light receiving device, and a driving part for moving an optical member in order to adjust an optical path difference between the first split light and the second split light; a mode switching unit that issues a mode switching signal for switching a measurement mode between at least two measurement modes including a first measurement mode for measuring the ocular axial length of the examinee's eye while moving the optical member at a first scanning rate, and a second measurement mode for measuring the ocular axial length of the examinee's eye while moving the optical member at a second scanning rate which is slower than the first scanning rate; and a calculation and control unit that performs operations of changing a scanning rate of the optical member at the time of measurement in accordance with the mode switching signal issued by the mode switching unit, controlling an operation of the driving part such that the optical member is moved at a scanning rate corresponding to the measurement mode switched by the mode switching unit, and measuring the ocular axial length of the examinee's eye, based on an output signal of the light receiving device, obtained at the time of moving the optical member.