A work support device disposed in a passage having a size enabling a user (M) to perform works, the work support device comprising: a measurement unit configured to measure an in-passage structure including an actual passage wall corresponding to an actual structure of the passage ; a correction unit configured to correct work position information to corrected work position information based on the in-passage structure and a designed in-passage structure, the designed in-passage structure including a designed passage wall corresponding to an ideal structure of the passage , the work position information being indicative of a work position in the designed in-passage structure, the corrected work position information being indicative of a work position in the in-passage structure; an irradiation control unit configured to control an irradiation unit to emit light indicative of a work region to be worked by the user (M), the light being emitted to a work position indicated by the corrected work position information; a first acquisition unit configured to acquire observation information of inside of the passage; a second acquisition unit configured to acquire reference position information of a predetermined reference position in the passage; and a structure calculation unit configured to calculate a structure of the actual passage wall based on the observation information and the reverence position information, wherein the correction unit is configured to correct the work position information based on the structure of the actual passage wall and a structure of the designed passage wall predetermined with reference to the reference position. a measurement unit configured to measure an in-passage structure including an actual passage wall corresponding to an actual structure of the passage ; a correction unit configured to correct work position information to corrected work position information based on the in-passage structure and a designed in-passage structure, the designed in-passage structure including a designed passage wall corresponding to an ideal structure of the passage , the work position information being indicative of a work position in the designed in-passage structure, the corrected work position information being indicative of a work position in the in-passage structure; an irradiation control unit configured to control an irradiation unit to emit light indicative of a work region to be worked by the user (M), the light being emitted to a work position indicated by the corrected work position information; a first acquisition unit configured to acquire observation information of inside of the passage; a second acquisition unit configured to acquire reference position information of a predetermined reference position in the passage; and a structure calculation unit configured to calculate a structure of the actual passage wall based on the observation information and the reverence position information, wherein the correction unit is configured to correct the work position information based on the structure of the actual passage wall and a structure of the designed passage wall predetermined with reference to the reference position. <EOS>