A preliminary processing technology for a sample locally cuts out a sample part of a device to be analyzed and processes it into a needle-like projection, and a technology of realizing SAP analysis on an atomic level by ensuring stabilized ion evaporation sequentially even in the case of a sample of multilayer structure including an element layer of small evaporation electric field. The preliminary processing method for a sample used on atom probe apparatus comprises a step for cutting the desired observing part of the sample into a block using an FIB equipment, a step for transferring the sample block onto a sample substrate and fixing the sample block in place, and a step for processing the sample block fixed onto the sample substrate into a needle-point shape by FIB etching. The sample processed into a needle-point shape is shaped such that the layer direction of the multilayer structure becomes parallel to the longitudinal direction of the needle.