The main share index fell 0.25 percent, or 14.35 points, to close at 5,672.64, its lowest close since March 6. It has fallen 2.8 percent over the last five sessions, mainly due to concerns over the rupee which hit a record low last week.
'The rupee depreciation will not encourage any foreigners to invest in shares. It will also increase the cost of many companies as most of the inputs are imported,' a stockbroker said.
The rupee traded little changed on Friday and dealers said the central bank had directed the market not to trade the currency beyond a certain level, but it remained under downward pressure.
The currency had hit an all-time low last week on panic buying by importers, but has recovered since then.
The bourse is at an oversold territory, with the 14-day Relative Strength Index on Friday at 25.688, below its lower neutral level of 30, Thomson Reuters data showed.
Shares in Ceylon Tobacco fell 3.79 percent to 1,116.60 rupees, while top conglomerate John Keells Holdings Plc fell 0.57 percent to 209.40 rupees.
Friday's turnover was 249.3 million rupees ($1.87 million), less than a third of this year's daily average of about 889.6 million rupees.
Foreign investors were net sellers for the third straight session, selling 3.38 million rupees worth of shares, but they have been net buyers of 18.49 billion rupees in stocks so far this year.
($1 = 133.0500 Sri Lanka rupees)
(Reporting by Ranga Sirilal and Shihar Aneez; Editing by Jijo Jacob)
(Reuters Messaging: firstname.lastname@example.org)(twitter.com/rangab a)