The use of magnetic material can improve the performance of a single-flux-quantum device by inducing high self-or mutual inductance, which can reduce the size or increase the sensitivity of the device. We used magnetic nanoparticles as the magnetic material and adopted photoresist patterns with Fe3O4 nanoparticles as a means of inserting nanoparticles into a device. The effect of the nanoparticles was investigated for SQUIDs with photoresist patterns. Analytical estimation of the effect indicated a variation in SQUID inductance of less than 1%, which is in agreement with the experimental results in the absence of external magnetic fields. On the other hand, when external DC magnetic fields were applied, a slight increase in inductance was observed for several SQUIDs.