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The effect of hydrogen on the structural change of vacancies in tungsten is analyzed by molecular dynamics in order to clarify the interaction between vacancies and hydrogen in tungsten. Simulations are performed at different temperatures (573, 773, 1073 K) and with different numbers of hydrogen in the vacancies (0, 18, 36, 54). Evaluating (1) isopotential surface for the increase of total potential energy, (2) the root mean square deviation (RMSD) of tungsten atoms, (3) the root mean square fluctuation (RMSF) of tungsten atoms and (4) density distribution in radial direction, we found that the presence of a large number of hydrogen in a vacancy at each temperature caused changes in the structure. This fact partially supports the experimental fact that in the coalescence of two tungsten vacancies, the retention of hydrogen activates them.