A knock determination apparatus for an internal combustion engine including an in-cylinder pressure sensor that is installed in each cylinder and detects an in-cylinder pressure, the knock determination apparatus characterized by comprising: knock intensity calculation means configured to calculate a knock intensity value that is a peak value of an intensity of a knock determination signal in a predetermined crank angle range including a range in which knock is likely to occur, based on an output signal from the in-cylinder pressure sensor; knock determination means configured to determine that when the knock intensity value calculated by the knock intensity calculation means is larger than a knock determination threshold value, knock has occurred; integrated intensity calculation means configured to calculate an integrated intensity value that is an integrated value of knock intensity values that are equal to or larger than a predetermined knock intensity threshold value among knock intensity values that are calculated at respective combustion cycles during a predetermined plurality of combustion cycles in a same cylinder; and correction means configured to correct the knock determination threshold value so that a difference between the integrated intensity value calculated by the integrated intensity calculation means and a target integrated intensity value decreases, wherein the predetermined knock intensity threshold value corresponds to a knock intensity which lies within a boundary region comprising a maximum predetermined percentage of knock intensity values in a frequency distribution relating the knock intensity values acquired in a predetermined plurality N of combustion cycles in the same cylinder when the internal combustion engine is operated in a state in which a knock level specified in accordance with a knock intensity value and a knock frequency is at a target knock level, and calculated frequencies of respective knock intensity values, and wherein the target integrated intensity value is an integrated value of knock intensities that are equal to or larger than the predetermined knock intensity threshold value and that are extracted from the knock intensity values acquired in the predetermined plurality of N combustion cycles in the same cylinder when the internal combustion engine is operated in the state in which the knock level is the target knock level. knock intensity calculation means configured to calculate a knock intensity value that is a peak value of an intensity of a knock determination signal in a predetermined crank angle range including a range in which knock is likely to occur, based on an output signal from the in-cylinder pressure sensor; knock determination means configured to determine that when the knock intensity value calculated by the knock intensity calculation means is larger than a knock determination threshold value, knock has occurred; integrated intensity calculation means configured to calculate an integrated intensity value that is an integrated value of knock intensity values that are equal to or larger than a predetermined knock intensity threshold value among knock intensity values that are calculated at respective combustion cycles during a predetermined plurality of combustion cycles in a same cylinder; and correction means configured to correct the knock determination threshold value so that a difference between the integrated intensity value calculated by the integrated intensity calculation means and a target integrated intensity value decreases, wherein the predetermined knock intensity threshold value corresponds to a knock intensity which lies within a boundary region comprising a maximum predetermined percentage of knock intensity values in a frequency distribution relating the knock intensity values acquired in a predetermined plurality N of combustion cycles in the same cylinder when the internal combustion engine is operated in a state in which a knock level specified in accordance with a knock intensity value and a knock frequency is at a target knock level, and calculated frequencies of respective knock intensity values, and wherein the target integrated intensity value is an integrated value of knock intensities that are equal to or larger than the predetermined knock intensity threshold value and that are extracted from the knock intensity values acquired in the predetermined plurality of N combustion cycles in the same cylinder when the internal combustion engine is operated in the state in which the knock level is the target knock level.