The invention discloses an internal combustion engine knock determination device and an ignition control system including the same. An engine ECU executes a program including the steps of: detecting a waveform of vibration of an engine at a predetermined knock detection gate (S100); determining whether a detected vibration's waveform and a knock waveform model stored in memory match within a predetermined range; if the model and the detected vibration's waveform match within the predetermined range (YES at S102), determining that the engine knocks (S104); and if the model and the detected vibration's waveform do not match within the predetermined range (NO at S102), then determining that the engine does not knock (S108).