The incident occurred in January 2016 and left a worker with a serious head injury.
LD Operations provided labour and services to the mine operator and was the employer of the injured worker.
Judge David Russell found the potential consequences of the incident were very serious and there were steps available to the defendant to eliminate or minimise the risk.
The worker was seriously injured while driving a loader underground at the colliery, when a damaged support strap hanging from the roof struck the man's head near his left eye.
The incident left the employee with a severe head laceration, which required medical treatment.
At the time of the incident, the mine was in a state of care and maintenance.
NSW Resources Regulator director of compliance Steve Orr said the judgement reflected community standards expected of mine safety.
"The court's ruling sends a strong message that the community expects mine operators to protect their workers and comply with their work health and safety obligations," Orr said.
"This matter serves as a timely reminder to companies to ensure they have appropriate controls in place."
The conviction and fine follows the regulator's prosecution of the mine operator LakeCoal Pty Ltd in relation to the same incident.
LakeCoal was convicted and fined $180,000 and ordered to pay the prosecutor's costs.