To provide a measurement data collection device and a measurement data collection system preventing failure in reading a data file during writing it for improvement in reliability of collection of measurement data.

This measurement data collection device is constructed of a measurement unit 2a periodically acquiring detection data from a sensor 2, a data file creation part 15 creating a data file consisting of dummy data, a file management control part 16 reading a FAT 4a from a memory card 4, storing the data file created by the data file creation part 15 in the memory card 4 based on the FAT, and writing allocation information about a storage area of the data file in the FAT 4a to store it in the memory card 4, and a file data replacement control part 13 accessing the memory card 4 based on the detection data to sequentially replacing the dummy data inside the data file, in which the allocation information is written in the FAT 4a, by the detection data.