When I tried to deploy rails files to EC2, An error occurred while installing pg is caused

I'd like to deploy my rails project using Capistrano3. Could you tell me how to deal withe the error? Thank you for your kindness.

When I tried to deploy, I got the following error message.

Deploy

cap production deploy

Erro code

bundle stdout: An error occurred while installing pg (0.18.2), and Bundler cannot continue.
Make sure that `gem install pg -v '0.18.2'` succeeds before bundling.

When I typed like this,

   [ec2-user@ip-172-31-47-193 ~]$ gem install pg -v '0.18.2'

I got the following error.

Building native extensions.  This could take a while...
ERROR:  Error installing pg:
ERROR: Failed to build gem native extension.

/home/ec2-user/.rbenv/versions/2.2.2/bin/ruby -r ./siteconf20150731-20195-11x65kw.rb extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
 --with-pg-config=/path/to/pg_config
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/home/ec2-user/.rbenv/versions/2.2.2/bin/$(RUBY_BASE_NAME)
--with-pg
--without-pg
--enable-windows-cross
--disable-windows-cross
--with-pg-config
--without-pg-config
--with-pg_config
--without-pg_config
--with-pg-dir
--without-pg-dir
--with-pg-include
--without-pg-include=${pg-dir}/include
--with-pg-lib
--without-pg-lib=${pg-dir}/lib

extconf failed, exit code 1

Gem files will remain installed in /home/ec2-user/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/pg-0.18.2 for inspection.
Results logged to /home/ec2-user/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/extensions/x86_64-linux/2.2.0-static/pg-0.18.2/gem_make.out