A tomographic image creation apparatus includes a time difference calculation unit, a signal waveform processing unit, an error estimation unit, a γ-ray pair generation position calculation unit, and an image creation unit. The time difference calculation unit calculates, for each of γ-ray pair coincidence events, a time difference of a timing at which a value of each of a first signal and a second signal output from a signal waveform acquisition unit reaches a threshold value. The signal waveform processing unit relatively shifts a waveform of the first signal or a waveform of the second signal by the time difference in a direction approaching each other. The error estimation unit estimates an error of the time difference by a DNN based on the waveform of each of the first signal and the second signal after shifting.