An image recording apparatus (1100, 1100', 2100, 2200, 3100) comprising: an image-data acquiring unit configured to sequentially acquire image data obtained by imaging a periphery of a vehicle (1900, 1900', 2900, 3900); an event-signal acquiring unit configured to acquire an event signal indicating occurrence of an event regarding a collision between the vehicle (1900, 1900', 2900, 3900) and another vehicle (1910, 2910, 3910); a condition detecting unit configured to detect, when the event-signal acquiring unit acquires the event signal, whether a positional relation of the other vehicle (1910, 2910, 3910) with the vehicle (1900, 1900', 2900, 3900) satisfies a condition, wherein the condition detecting unit is configured to serve as a position detecting unit (1140, 2140), and the position detecting unit is configured to detect whether a position of the other vehicle (1910, 2910, 3910) appearing in an image in the image data acquired by the image-data acquiring unit satisfies a predetermined positional relation and to detect, when it detects the position of the other vehicle (1910, 2910, 3910) satisfies the predetermined positional relation, that the condition is satisfied, wherein the predetermined positional relation is a positional relation in which the other vehicle (1910, 2910, 3910) is separated from the vehicle (1900, 1900', 2900, 3900) such that a road surface (1920, 2920) is detected between the vehicle (1900, 1900', 2900, 3900) and the other vehicle (1910, 2910, 3910) in the image, or wherein the predetermined positional relation is a positional relation in which an entire image of the other vehicle (1910, 2910, 3910) is recognized in the image; and a writing controller configured to write the image data in a memory in a ring buffer format, and to write, when the event-signal acquiring unit acquires the event signal, the image data including a period from when the event signal has been acquired until the condition detecting unit has detected that the condition is satisfied in the memory such that the image data is not overwritten. an image-data acquiring unit configured to sequentially acquire image data obtained by imaging a periphery of a vehicle (1900, 1900', 2900, 3900); an event-signal acquiring unit configured to acquire an event signal indicating occurrence of an event regarding a collision between the vehicle (1900, 1900', 2900, 3900) and another vehicle (1910, 2910, 3910); a condition detecting unit configured to detect, when the event-signal acquiring unit acquires the event signal, whether a positional relation of the other vehicle (1910, 2910, 3910) with the vehicle (1900, 1900', 2900, 3900) satisfies a condition, wherein the condition detecting unit is configured to serve as a position detecting unit (1140, 2140), and the position detecting unit is configured to detect whether a position of the other vehicle (1910, 2910, 3910) appearing in an image in the image data acquired by the image-data acquiring unit satisfies a predetermined positional relation and to detect, when it detects the position of the other vehicle (1910, 2910, 3910) satisfies the predetermined positional relation, that the condition is satisfied, wherein the predetermined positional relation is a positional relation in which the other vehicle (1910, 2910, 3910) is separated from the vehicle (1900, 1900', 2900, 3900) such that a road surface (1920, 2920) is detected between the vehicle (1900, 1900', 2900, 3900) and the other vehicle (1910, 2910, 3910) in the image, or wherein the predetermined positional relation is a positional relation in which an entire image of the other vehicle (1910, 2910, 3910) is recognized in the image; and a writing controller configured to write the image data in a memory in a ring buffer format, and to write, when the event-signal acquiring unit acquires the event signal, the image data including a period from when the event signal has been acquired until the condition detecting unit has detected that the condition is satisfied in the memory such that the image data is not overwritten.