Nominal pay checks rose 1.2 percent from 2012 to 2014, the Neuchâtel-based FSO said in a report.
At the same time, pay for senior managers — those in the top 10 percent of management — dropped to 18,939 francs a month in 2014 from 23,444 in 2012, the report said.
Salaries for workers, among the highest in the world, ranged considerably, according to the field people were employed in.
Median salaries in the financial sector amounted to 9,549 francs a month, for example, while employees in the pharmaceutical industry earned a median wage of 9,694 francs a month.
At the lower end of the scale, were food industry workers (5,303 francs) and those employed in retail (4,761 francs), hotels and restaurants (4,333 francs) and personal services (3,910 francs), the FSO said.
The bottom ten percent of salaried workers earned less than 4,178 francs per month, while the best paid ten percent received more than 10,935 francs.
The gap between the highest and lowest groups narrowed, however, the report said.
Workers in Switzerland typically receive an extra month's salary in December, resulting in 13 monthly payments per year.
Daniel Lampart, secretary of the Swiss Federation of Trade Unions, told broadcaster RTS that the figures showed workers had been able to successfully resist pressure from employers to cut wages because of the strong franc (versus the euro).
However, the increase between 2012 and 2014 was more modest that between 2010 and 2012 when median pay rose 3.2 percent, the FSO said.
Figures showed that the pay gap between men and women narrowed, although male workers still received 15.1 percent more than females last year, compared to 18.9 percent more in 2012.
The FSO said the gender pay gap was more noticeable for highly qualified positions.
In positions of significant responsibility, for example, women earned an average of 8,221 francs a month, while men in the same kind of posts earned 10,553 francs, 22 percent more.
The report showed that foreigners in top positions on average earned more than their Swiss counterparts while the reverse was true for jobs involving lower levels of responsibility.