The OMXS index was up 3.2 percent to 392.3. The narrower OMXS-30 index rose by 3.6 percent.
A strong report from US investment bank Lehman Brothers helped calm markets on Wednesday, following the recent period of concern over the international financial system.
The Stockholm market rose by 3 percent in opening trading, strengthening further towards the end of the day. Nearly all sectors benefited from the rises, with heavy industry coming out best. Atlas Copco was up 7.5 percent to 107 kronor. Ball bearing manufacturer SKF rose 6.2 percent to 136.25 kronor.
Shares in stock market operator OMX fell by 7.1 percent to 240.50 kronor before trading in the company was suspended late in the afternoon. More information was due to be released on Thursday about the reason for the suspension.