jQuery.extend(jQuery.easing,
{
  easeOutQuart: function (x, t, b, c, d) {
		return -c * ((t=t/d-1)*t*t*t - 1) + b;
	},
});

(function($) {
	$.fn.smoothscroll = function(option) {
		var settings = $.extend({
			speed: 1000
		}, option);

		$(this).click(function() {
			$('html, body').animate({
				scrollTop: $(this.getAttribute('href')).length ? $(this.getAttribute('href')).offset().top : 0
			}, settings.speed, 'easeOutQuart');

			return false;
		});

		return this;
	};
})(jQuery);
$(document).ready(function() {
			$('a[href^=#]').smoothscroll({
				speed: 1000 //1秒かけて移動
			});
		});