* Shares open at $18.50, above IPO price of $16
* Co valued at $1.32 bln at day's high of $19.39
(Add details, updates shares)
March 27 (Reuters) - Shares of cloud-based payroll processor TriNet Group Inc rose as much as 21 percent in their market debut, valuing the company at about $1.32 billion.
The San Leandro, California-based company raised about $240 million after its initial public offering was priced at $16 per share, the mid point of its expected range.
TriNet's shares opened at $18.50 and touched a high of $19.39, making the stock the percentage gainer on the New York Stock Exchange on Thursday.
More than 5 million shares changed hands by 1100 ET.
Stake of General Atlantic, one of the company's top stockholder, will be diluted to about 56 percent after the offering from 71.4 percent, TriNet said in a filing with the U.S. Securities and Exchange Commission.
Last week, online payroll processor Paylocity Holding Corp's shares rose as much as 80 percent in their market debut as offerings by cloud-based enterprise software companies continue to rule the IPO market.
TriNet expects to tap the growing demand from small- and medium-sized businesses which outsource their payroll, employee-benefit and other human resources functions.
The company, which counts TotalSource unit of Automatic Data Processing Inc and Insperity Inc among its competitors, had more than 8,900 clients as of Dec. 31.
TriNet bought HR services company Ambrose Employer Group LLC, technology firm App7 Inc and insurance and risk-management service provider Gevity HR Inc in the last five years.
The company said revenue rose 61 percent to $1.64 billion in 2013 while net income fell 58 percent to $13.1 million.
TriNet is headed by 58-year-old Burton Goldfield, who had served as chief executive of Ketera Technologies Inc, a business management software company.
JP Morgan, Morgan Stanley and Deutsche Bank were lead underwriters to the offering.
(Reporting By Neha Dimri in Bangalore; Editing by Kirti Pandey and Don Sebastian)