Abase material processing apparatus comprising: a transport mechanism that transports a long band-like base material in a longitudinal direction along a predetermined transport path; a first detector that successively or intermittently detects a position (Pa) of an edge of the base material in a width direction at an upstream detection position in the transport path to acquire a first detection result; a second detector that successively or intermittently detects the position of the edge of the base material in the width direction at a downstream detection position (Pb) located downstream of the upstream detection position in the transport path to acquire a second detection result; characterized by a displacement amount calculation part that, for each of a plurality of upstream data sections that are data sections included in the first detection result, is configured to identify a highly matched downstream data section from among a plurality of downstream data sections that are data sections included in the second detection result, and to calculate an amount of displacement of the base material in a transport direction or an amount of difference in a transport speed of the base material on the basis of an identification result, wherein each of the plurality of upstream data sections (D1, D2) includes a plurality of upstream sub-data sections (d11 to d18, d21 to d28), each of the plurality of downstream data sections includes a plurality of downstream sub-data sections, and the displacement amount calculation part is configured to use at least one result obtained by sequentially calculating a degree of matching between one of the plurality of upstream sub-data sections (d11 to d18) and one of the plurality of downstream sub-data sections (d21 to d28) to identify the highly matched downstream data section for each of the plurality of upstream data sections. a transport mechanism that transports a long band-like base material in a longitudinal direction along a predetermined transport path; a first detector that successively or intermittently detects a position (Pa) of an edge of the base material in a width direction at an upstream detection position in the transport path to acquire a first detection result; a second detector that successively or intermittently detects the position of the edge of the base material in the width direction at a downstream detection position (Pb) located downstream of the upstream detection position in the transport path to acquire a second detection result; characterized by a displacement amount calculation part that, for each of a plurality of upstream data sections that are data sections included in the first detection result, is configured to identify a highly matched downstream data section from among a plurality of downstream data sections that are data sections included in the second detection result, and to calculate an amount of displacement of the base material in a transport direction or an amount of difference in a transport speed of the base material on the basis of an identification result, wherein each of the plurality of upstream data sections (D1, D2) includes a plurality of upstream sub-data sections (d11 to d18, d21 to d28), each of the plurality of downstream data sections includes a plurality of downstream sub-data sections, and the displacement amount calculation part is configured to use at least one result obtained by sequentially calculating a degree of matching between one of the plurality of upstream sub-data sections (d11 to d18) and one of the plurality of downstream sub-data sections (d21 to d28) to identify the highly matched downstream data section for each of the plurality of upstream data sections.