A sample clock generator for an optical tomographic imaging apparatus configured to receive a frequency-swept input light emitted from a light source and to generate a sample clock signal, the sample clock generator comprising: an interference optical system at least comprising: a first optical path through which part of the input light is guided; a second optical path through which other part of the input light is guided; an optical phase shifter to shift a phase of the input light guided through the first optical path; an interference-light generating unit to combine the input light guided through the first optical path and phase-shifted and the input light guided through the second optical path, to thereby generate an interference light for sample clock; and a splitting unit to split the interference light for sample clock into one linearly-polarized light and another linearly-polarized light that is mutually perpendicular to the one linearly-polarized light; and an operation unit at least comprising: one light receiving unit to at least receive the one linearly-polarized light; another light receiving unit to at least receive the other linearly-polarized light; and a signal generating unit to generate the sample clock signal by performing an exclusive OR operation based on signals outputted from the one light receiving unit and the other light receiving unit, wherein the optical phase shifter shifts a phase of the input light such that a phase difference of a 1/4 wavelength or a 1/8 wavelength exists between the one linearly-polarized light and the other linearly-polarized light. an interference optical system at least comprising: a first optical path through which part of the input light is guided; a second optical path through which other part of the input light is guided; an optical phase shifter to shift a phase of the input light guided through the first optical path; an interference-light generating unit to combine the input light guided through the first optical path and phase-shifted and the input light guided through the second optical path, to thereby generate an interference light for sample clock; and a splitting unit to split the interference light for sample clock into one linearly-polarized light and another linearly-polarized light that is mutually perpendicular to the one linearly-polarized light; and a first optical path through which part of the input light is guided; a second optical path through which other part of the input light is guided; an optical phase shifter to shift a phase of the input light guided through the first optical path; an interference-light generating unit to combine the input light guided through the first optical path and phase-shifted and the input light guided through the second optical path, to thereby generate an interference light for sample clock; and a splitting unit to split the interference light for sample clock into one linearly-polarized light and another linearly-polarized light that is mutually perpendicular to the one linearly-polarized light; and an operation unit at least comprising: one light receiving unit to at least receive the one linearly-polarized light; another light receiving unit to at least receive the other linearly-polarized light; and a signal generating unit to generate the sample clock signal by performing an exclusive OR operation based on signals outputted from the one light receiving unit and the other light receiving unit, one light receiving unit to at least receive the one linearly-polarized light; another light receiving unit to at least receive the other linearly-polarized light; and a signal generating unit to generate the sample clock signal by performing an exclusive OR operation based on signals outputted from the one light receiving unit and the other light receiving unit, wherein the optical phase shifter shifts a phase of the input light such that a phase difference of a 1/4 wavelength or a 1/8 wavelength exists between the one linearly-polarized light and the other linearly-polarized light.