This paper estimates individual‐level matching functions to measure search frictions in the Japanese labour market and presents the determinants of search duration. We employ administrative microdata that track the job search process of job seekers who left or lost their job in August 2005 and subsequently registered at their local public employment service. Our finding is that the matching function exhibits decreasing rather than constant returns‐to‐scale for job seekers and vacancies. We also find that after controlling for the benefits period, job seekers who lost their job involuntarily were more likely than those quitting voluntarily to exit from unemployment.