1. A simulation apparatus which simulates a position of each of a plurality of objects, which move in a virtual space together with time, at each of a plurality of points of time of calculation, comprising: an object pair information acquisition unit configured to acquire a plurality of pieces of information of object pairs each including, as components thereof, two objects which contact with each other at each of the plural points of time of calculation; an allocation unit configured to allocate, at each of the plural points of time of calculation, each of the plural object pairs corresponding to the acquired information to one of a plurality of groups such that two or more object pairs which include a common object do not belong to the same group; and a calculation unit configured to calculate, at each of the plural points of time of calculation, an influence of contact of two objects included in each of the plural object pairs corresponding to the acquired information upon positions of the two objects; the calculation unit executing the calculations of the object pairs in parallel to each other while preventing the calculations for the object pairs which belong to groups different from each other from being executed in parallel to each other; the allocation unit referring, when the allocation of an object pair at the present point of time of calculation is carried out, to allocation information when the object pairs were allocated to a plurality of groups at the immediately preceding point of time of calculation to determine allocation of the object pairs such that object pairs between which the two components are common at the immediately preceding point of time of calculation and at the present point of time of calculation belong to a group same as the group to which the two components were allocated at the immediately preceding point of time of calculation.