Increased inductance values and contact resistance in connector contact surfaces due to degradation of connector contact performance have been reported. In particular, inductance increases while degradation remains minimal. We focus on slight loosening in which increased inductance values are observed without increased resistance values, and investigate the effect of loose connectors on transmission line coupling noise under such circumstances. We find a proportional relation between coupled noise current and frequency. Moreover, we find a proportional relation between the increased inductance value, which depends on the change in connector contact distribution, and the coupled noise current in the transmission line.